Paint and Body Frame rail dimensions

keel · Jan 30, 2026

I'm currently in the process of repairing some relatively minor crash damage on my 1993 LX and I am replacing the front core support. I have a replacement core support from LMR but it doesn't fit properly. The frame rails are maybe about half an inch too far apart for the core support to be installed easily.

I'm wondering if maybe my rails spread apart slightly and I'm hoping someone has some dimensions I can use to check whether or not my car is messed up or if the core support I got is defective. Also some advice on how to fix this kind of thing would be greatly appreciated too.

I did cut the old core support in half to make it easier to remove from the car and it didn't spring apart or anything so I'm not really sure whats going on.

Attached is a pic of the crash damage. Doesn't seem like it could tweak the frame rail but I know these cars are notoriously fragile.

KRUISR · Jan 30, 2026

I don't know if they would apply directly to your '93, but should get you in the ballpark of square. Not sure where they came from but I downloaded them from the internet over the years.

AeroCoupe · Jan 30, 2026

Same. You can use the subframes from another car up to I think 2004. I know subframe connectors work from 79-2004 and I know I read this somewhere on here in a couple threads.

Mustang5L5 · Jan 31, 2026

AeroCoupe said:
Same. You can use the subframes from another car up to I think 2004. I know subframe connectors work from 79-2004 and I know I read this somewhere on here in a couple threads.

You can. I fixed my strut tower/rail rot with a donor new edge rail/tower on one side.

AeroCoupe · Jan 31, 2026

Well that makes me feel better that I did read that from a reputable source.

KRUISR · Jan 31, 2026

I used a frame rail from a '97 V6 to repair the driver frame rail on my son's '89. Only thing is the bolt hole locations for the k-member are off slightly. I think I moved them 5/8" rearward. I kept the k-member in place and used it as a template to align the bolt holes.

Mustang5L5 · Jan 31, 2026

AeroCoupe said:
Well that makes me feel better that I did read that from a reputable source.

Fun stuff.

Only change I had to make was relocate the K-member bolt holes

keel · Feb 2, 2026

If my rail is spread outward a little bit do you guys think I could just bend it back to position to fit the core support? Or is that just gonna cause other issues with panel alignment or the way it drives? It just seems like a lot of work that I don't necessarily want to invest in order to replace the entire rail.

Just to be clear I am not super attached to this chassis and I don't need it to be perfect. I just want the car to drive properly and look relatively presentable.

KRUISR · Feb 2, 2026

Is it the frame rail or the upper structure that has spread? Pics help here.

Based on the dimensions shown above, where and by how much are you out?

keel · Feb 2, 2026

You wouldn't really be able to tell anything from a picture since it looks completely fine visually. The rails are a half inch too wide where it is supposed to mate up to the core support and so it won't slide into place without forcing it in. I could definitely install it with brute force but it's not really ideal.

It's tough to tell anything other than that from measuring because it's not off by much and the motor is still in the car. Plus I didn't take any measurements before I pulled the core support.

Upper structure also got damaged so I will probably cut out and replace the inner fender apron but that won't fix the bigger issue which is the frame rail alignment to the core support.

KRUISR · Feb 2, 2026

Well, the pics will help those you are asking for help to understand where you are at, what you have removed and what you are trying to install.

If you are out by at least 1/2" there is likely a sign or indication (a kink or bend on the inside or outside face of the frame rail).

Pics of the rails allows those of us that have repaired our frame rails, looked for the signs of damage and measured to keep them square to see things maybe you haven't and point you in the direction to solve your problem. Don't worry if you have ugly parts of your car you are embarrassed to show, we have all been there - some still are.

AeroCoupe · Feb 2, 2026

If you try to pull them in be sure to loosen the k-member. I would do this regardless and reset it between the shock towers being it was hit it could be off as well.

keel · Feb 2, 2026

Okay got some pics. I measured between the tooling holes that I circled in red and I got 35.25" which I think is actually in spec unless I am misunderstanding the diagram that was posted by @KRUISR. Also did not notice any kinks or bends in the rail. What do you guys think?

KRUISR · Feb 2, 2026

I believe that dimension is correct. What are your measurement when you measure at the top area, triangulate to the strut mount bolts?

Is your issue mentioned above that the donor rad support will not fit into the frame rails? What year did your donor part come from? If you don't know, post a pic because there are some differences over the years.

I found another frame drawing...

Not sure if the holes referenced in this drawing are on the top or bottom of the frame rail (I don't have access to a foxbody right now to check - or measure), but the 35-3/16" is smaller than what you measured. I would guess on the bottom as it would be easier to check some of the measurements going back to k-member mounts or trans mount area.

From the drawing that has measurements along the top, try and find to front holes on each side (I would use the reference measurements from a hole at rear of engine bay and/or strut top plate bolt holes) and check for that 47-13/16" across the front. Its possible the top has bowed out as well.

keel · Feb 2, 2026

The rad support I got is the OE replacement sold by LMR for a 90-93 car. I did find it on FB marketplace which could mean that the part itself is suspect but it doesn't look like anyone ever tried to install it before I got my hands on it.

https://lmr.com/item/LRS-16138A/90-93-Mustang-Radiator-Core-Support

I'll take some more measurements when I have time tomorrow.

Mustang5L5 · Feb 3, 2026

More info. My docs say this applies to 1993.

Mustang5L5 · Feb 3, 2026

My records say this is 1988. I think this may apply to 87-89 only as some stuff changed in 1990, so consider this reference only.

keel · Feb 10, 2026

Alright it took me a little longer to make progress than I was planning but here is the update. I wasn't really able to measure much because the engine is in the way and what I was able to measure wasn't out of spec enough for me to draw any clear conclusions since I was using a tape measure and I'm sure the tolerances when they were assembling these things weren't exactly aerospace levels of precision.

Here is the solution I came up with to get the core support to fit properly:

I used a ratchet strap to pull the rails inward and it ain't pretty but I only needed to move the frame rails about a quarter inch closer together to get this to work. It should be good enough to achieve the results I'm looking for. Other than that everything fit pretty well.

The areas where the core support meets the top of the inner fender apron are a little uneven but not too bad. What do you guys think? Is there anything I can do relatively easily to get it to line up a little better? I have good contact on all the surfaces that need to be welded except there is a small gap where the frame rail butts up against the core support that is visible in the pictures.

KRUISR · Feb 11, 2026

The dimension of these gaps on each side of the core support on my son's '89 GT were not the same from the factory. I would assume that could still be the case with the '93s. I will take a couple of pics later today and include them here. If you need any other dimensions measured I have access to the car this until the weekend.

AeroCoupe · Feb 11, 2026

Calling @95steedamustang

Paint and Body Frame rail dimensions

keel

Active Member

Attachments

KRUISR

AeroCoupe

lube between the nut and the face. I know my lubes

Mustang5L5

That is…until I whipped out my Bissell

AeroCoupe

lube between the nut and the face. I know my lubes

KRUISR

Mustang5L5

That is…until I whipped out my Bissell

keel

Active Member

KRUISR

keel

Active Member

KRUISR

AeroCoupe

lube between the nut and the face. I know my lubes

keel

Active Member

Attachments

KRUISR

keel

Active Member

Mustang5L5

That is…until I whipped out my Bissell

Mustang5L5

That is…until I whipped out my Bissell

keel

Active Member

KRUISR

AeroCoupe

lube between the nut and the face. I know my lubes

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Paint and Body Frame rail dimensions

Active Member

Attachments

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

Active Member

Active Member

lube between the nut and the face. I know my lubes

Active Member

Attachments

Active Member

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

Active Member

lube between the nut and the face. I know my lubes

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