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

If you were running a 741 (small pinion shaft) rear with a 4 speed and sticky tires I would have serious concerns but not with the 742 or 489. My only advise is to go with a drive shaft loop, even if you are running it on the street mostly, just for piece of mind. They're a lot cheaper and easier to install than a Dana.

Terry