What tranny to use?
 

I building a 1977 ford F250 4x4 to be a stock pulling truck and it going to get a 514 engine i thought about running a C6 but now a wonder if I should stick with the 4 speed that is in it but I dont know if the engine will tear up things with the 4 speed or not and I dont know if a c6 will last that long doing that

What tranny to use?