GM to Mopar trans swap?!

Was that a fully synchronized A-230? That 230 has a generous mainshaft. Where did it let go?
If you can break one of those, the only cure is an a-833.
That 84Buick is a FWD. The last year of the 5 speed was 1980.And it was designed for 110, countem 110 ponypower.
The FWD 5spds were designed for 80 to 90 miserable ponies.

What in the world are you thinking?