A member here bought my 68 D100 stepside that was a slant 3-speed and he put a 440 in it, something I always wanted to do! It is an easy swap, but you will need to get a 69-71 trans crossmember. I have a factory 69 D200 383 truck and there is plenty of room to play.
The funny thing about science is that if you change one miniscule parameter you change the entire outcome to the way you want it.
