1965 mustang body work, Complete Floor Pan Assembly install questions

Hi everyone. I haven't logged on in a really long time.

Long story shorter (back story part), life got in the way with my Father/Son 1965 mustang project. (I'm the son. My dad is the body shop guy, 20 years of collision repair.)

Most of the work I'm talking about was done 10 plus years ago.

The car is a standard rust belt car, that looks like it got rear ended and got new (1966 maybe?) quarters/tail welded on. (Didn't know this until we tore the car apart.)

We took off all bolted on parts.

Cut off the engine bay.

Cut out the firewall. (Not that it attached much other than at the top.)

Cut out any remain floor/trunk pan. (The floor was scary bad, but had more metal riveted to it. It did have to go.)

(All above cut out were saved for extra parts and points of reference.)

Sounds like a lot cut out? Well, it was. It is a dash/A pillar, roof to rear quarters and trunk of a car. The car, if you can even call it that, is braced in place. (On a make shift 1990s style car body liner.) Been this way for years. Driver side cowl repair completed in the past years at some point.

I think WAY too much was cut out at once, but that is water under the bridge. Can't undo it now.

We have a full floor pan (with front AND rear frame rails, trunk, etc) to install, and a new firewall. Also left/right engine bay assemblies. (Shock tower with aprons to either side. Will need lots of parts off the old one. I wanted to save the old one.)

Floor pan is either this one, or just like it. (I had a thread here years ago about repainting it as it got rust on it just sitting in the garage.)


The problem:

My dad expected more body manuals and points of reference to exist on how to weld all of this back together. Mostly on the where to measure point A reference to point B reference for positioning the full floor pan assembly in the correct spot to the outer rockers, trunk, wheel wells, etc.

We still need to peel off the inner rockers (full pan assembly has them) and weld the new full floor pan assembly in.

It he over thinking this? (He thinks the placement needs to be more exact than 1/4" for example. I have no idea how exact, this isn't my area of expertise.)

I'm thinking, you just put it in place and line everything up? (Trunk & bumper points to each other and everything. Rockers all line up, etc. Center the up/down on inner/outer rockers to each other. Back to match the trunk lines. The firewall and engine bay can be fit to the front side when they go back on.

In my quick searching, it looks like member Ryan Miller might have installed one of these. But, he still had an engine bay/firewall on the car.

Suggestions?

If anyone spit out their coffee while reading this and are laughing, feel free to take a picture of the mess and post it here.

At this point, I just want to get the car back together and drive able for my dad before he dies. (He isn't "dying" but he is old. And this could still take years.)

Thanks.

Edit: I did find these videos where he is trunk-less, while I'm engine bay-less. So, maybe we aren't too crazy.

part 1
View: https://www.youtube.com/watch?v=fgt2kZAOAU4

part 2
View: https://www.youtube.com/watch?v=B1he9El9bl4

There is no floor pan, all gone.

My dad's primary question is how high/low to put the new complete pan in. Easy match front to back.

What reference points do you use to level the car, and what point to level the floor pan? Than, what points to measure that the pan is at the correct height relative to the car when you weld it in?

Thanks for the links, I'll read through those next.

GOvert said:

I was up at 4:30 a.m. doing a breathing treatment so I wasn't entirely awake. I'm up again as I wake up, I will see if I can think through this again.
It would be nice to have access to another 1965 Mustang to use for general reference. However, keep this in mind. The several different assembly plants, San Jose, Dearborn and Metuchen were building Mustangs simultaneously within a 1/4" tolerance. So what looks the same may not be. I once "clipped" two halves of two Mustangs from different assembly plants and struggled all week with it because of the fact that the two were put together at the opposite edge of the tolerances.
You will need two 6' levels spanning the rockers from left side to right side and two 2' levels on top of each rocker front to back. Secure them somehow. Then to start with you need some jack stands that are threaded so that you can adjust them minutely. Some people have used house jacks. Always keep thinking about the box. The levels will need to be level sided to side with the long levels spanning the rockers and the short levels, level too. Level is parallel to the earth. As far as floor pan up down location is concerned, hopefully you haven't entirely cleaned all the old stuff off of the inside of you rockers that show where the floor pan use to be. Some floor pans the side lips turn up, some down. If they turn down the that helps. This lip in some cases is part of the rocker "pinch weld". That is if it points down. Also hope that the reproduction manufacturer made this lip even and consistent. Some older repro parts are crappy and a guide at best. So now you have your piece of sub body level and stable. You don't want it to shift off of level or you may have problems. That's why assembly jigs have sturdy attachment points.
If your floor pan IS NOT like the one in the picture below, purchase you one. It will save you thousands in head aches. It already has the rear part of the front frame rails, braces, seat boxes, under the back seat and trunk area all in place. The inner rockers are even attached to it. They have been assembled on a jig. Study the picture and you will see what I mean.

Click to expand...

Mine looks close to that.

We cut out the dual exhaust hangers (original GT car) and put them on the new pan. Seat mounting brackets too. Exchause the poor welds. I took a few classes, but my dad always makes me do them, even though he is way better.

Pictures attached.

GOvert said:

@runawayabc123 If your replacement floor pan has the inner rocker attached from the factory, you can simply square it up to the outer rocker to get your placement. The floor pan is already attached to the inner rocker, so there is your placement. The top of the inner rocker and the outer rocker line up. The bottom of the inner rocker and outer rocker line up. If you look at you post #3 picture where you are separating the inner and outer rocker, there is your answer.

Click to expand...

Thanks for the tip. We are going to try to put it in this weekend. We're using that and where the old one was and where the old floor pan was (but not much of that is left).

As an update, we got it in. (Just in, not welded yet.) Lots of jacking, pushing and hammering to get it to the right spot. Still needs some more leveling and fine tuning. I don't really want to do one of these again.

runawayabc123 said:

Thanks for the tip. We are going to try to put it in this weekend. We're using that and where the old one was and where the old floor pan was (but not much of that is left).

As an update, we got it in. (Just in, not welded yet.) Lots of jacking, pushing and hammering to get it to the right spot. Still needs some more leveling and fine tuning. I don't really want to do one of these again.

Click to expand...

Yes. It also has seat belt mounts on it too. Both of those had to be convinced to slip past the outer rocker when installing.