I just bought a 91 automatic fc and the transmission needs replaced as it currently will not drive and i’m not sure why. I plan to manual swap but i’m having a hard time finding a transmission anywhere near me. Am I able to use a transmission from the earlier years of the fc? Or does anyone know of any places I could look to find one.

 

short of the final gear ratio the S4 and S5 NA gear boxes are identical and should drop right in. Might be minor connector differences, but that's easy to circumvent.

for used parts, ebay and facebook marketplace are likely your best bets.

 

Crossmember will be different too. Not a huge deal.