rusty, if your going to keep the 55 case then do yourself a favor and get an early four speed, there is no benefit to the later four speed except the split case behind it.
heres the basic breakdown to put the 60 series 2F, tranny and split case in the pig. if your keeping the 55 case disregard some of these.
drill and tap holes in the bellhousing for the 55 type tranny mounts if you dont wanna mess with the 60 crossmember, everything is there and in the right place just need threaded holes. engine motor mounts the same.
trade the 60 series water pump and pully for the earlier style found in the 55, its about 1 1/2" too long for the pig.
need to relocate the tranny shifter hole in the hump back 2" to clear the shifter, transfer stick is fine.
rear driveshaft shortened, front is good.
then wiring for the elctric dizzy and alt unless you will use the 55 alt.
may need a little different plumbing for heater, vary upon years.
and thats all i can think of.