I am building a 302 out of 1978 ford f100 and I would like to use crank out of 1986 5.0 roller motor the only difference I can see is 5.0 has 1 piece seal and 78 has a 2 piece seal there is a small lip on the 78 crank were the seal rides that the 5.0 dosen't have should this be a problem I haven't purchased 2 piece seal yet to see what it looks like Thanks Mike

 

Use the 1-piece seal if at all possible. Crank balance is different too.. 28oz on the '78 and 50oz on the '85, which means you can't use whatever flywheel/flexplate you have now.