they common thing to go out on the c-4s is the clutch packs when juicing too much power through them.... i had one in my mustang before when i put a v8 in it and then quickly upgraded to a 6spd manual..... if you want a good strong tranny for that car and like manual then a 5spd out of a 4cyl 2.4 ranger will directly drop in your car and just need a clutch pedal and crossmember kit added.... your torque converter should be fine unless there were some broken hard parts that found their way into the converter but thats unlikely