My local transmission shop seems unable to work on my FMX trans from my '72 with 351C. Is there another hearty transmission with more parts available that could fit with minimal alterations?
If you tell us where you are located, someone might be able to tell you of a transmission shop in your area that could fix it.
Either the C4 or the C6 can be used in place of the FMX. The C6 was optional on your car. The C4 bolts up and works fine.
I found a '74 C4 from a 351W powered Cougar, it has a bigger torque convertor and bigger first gear synchro than typical c4(?) not a trans guy. It bolted in and uses 40 less HP than a c6. Also at least 100lbs lighter than FMX. Car feels nimble now, 1969 xr7 conv m code
Crossville TN. Closest bigger city is Knoxville.