Who knows B bodies very well ?

Are you saying the K member has to be swapped ?
NO I am saying that.... maybe the V8 suspension would be more worthwhile. It is not that hard to changeout the K and thus suspension. You need v8 suspension? as is maybe discs, T bat, etc?????

Going from slant to v8 you will want correct radiator and the 7 1/4 will maybe prove small. There are a millions threads on such swaps.