1987+ 350 with original 1964 3speed?

[1964FarmFreshC10]

I want to replace the original inline 6 230CI in my 1964 with a V8.

I have a running 350 TBI engine out of a 1989 Truck currently running a carb. I was reading yesterday about the difference in the crankshaft Internal vs external balance and the difference in bolt pattern for the flywheel/flexplate.

To make my life easier i was planning to keep the 3 on the tree for at least a year or 2 and then switch to an auto

Is it possible to use the original 3 on the tree with that engine or should i be looking for a pre 1986 350?