Driveshaft, Yoke and Rear Swap from 72 (C4) to 73 (FMX)?

[Platonic Solid]

I suspect the driveshaft of my 73 Mach may be damaged, causing severe highway vibration. I’ve come to this conclusion from seeing a major gouge in the sheetmetal tunnel directly above the rear U-joint. (previous owner damage).

Since I won’t be working on the 72 Coupe anytime in the near future, and I want to replace the leaf springs and shocks on the 73 anyway, I was thinking maybe I should swap the newly rebuilt 8” rear, driveshaft and yoke (with new U-joints) from the 72 Coupe (289, C4) into the 73 Mach (351C 2V, FMX, 9” rear).

Anyone know if this is a straightforward swap?
Will the Yoke from the C4 fit the FMX?
Are the driveshafts the same length? (Yeah, I know: I can get on the ground with a tape measure and check, but typing the question is sooo much easier )

Thanks

 

[HHStang]

don't know Svend, but I'll bump you. Seems like the fmx was c6-ish in length, but not sure. Could be as simple as changing the u joint cups or whatever they are called though. Mike

 

[dennis112]

C4 normally has a 28 spline yoke. Pretty sure the FMX has 31 splines similar to a C6.

 

[D.Hearne]

Ditto, FMX's are 31 spline. You need a yoke? I got a few spares.

 

[Platonic Solid]

Ditto, FMX's are 31 spline. You need a yoke? I got a few spares.

Cool. I don't want to re-use any of the old 73 driveshaft components, so if you have a good one for an FMX that you'd be willing to sell, (and it's convenient for you to get your hands on) I'm interested. [email protected]

... Could be as simple as changing the u joint cups or whatever they are called though.

It's actually easier for me to just swap the parts (if they fit). Considering the size of the gouge in the tunnel and the severity of the vibration, odds are the driveshaft is bent, or at least seriously out of ballance.

Thanks