Will my 8-3/4 hold up behind a 4 speed?

MSHRED, you should get your self some books and compare designs between manufacturers.
Some of the questions you ask sound like the byproduct of the advise a chevy guy gave you.
Just doesn't sound like a lot of faith i mopar to me.

If you simply look at factory SB & BB cars from chrysler you'd see that almost all high performance cars got the 8 3/4-[ex hemi 4spd=dana] and that was so the factory didn't have to worry about having to warranty anything.

You'll be fine.