8" rearends are allot stronger then they're given credit for. More parts are becoming available along with alum 3rd members. It's lighter then a 9" and when you lift the 3rd member you'll feel the difference. Gear selection is biggest drawback. But on the other side of the coin, it's not as confusing either. 3.00, 3.25, 3.55. 3.70s and 4.11 pretty much covers what you should need. My son's 72 Mav Grabber, I used an 8" with 4.11s and an AOD. Best of both worlds, IMO.
i put a 9 inch from a 57 Ranchero in my maverick, the best thing is that as long as the measurments are the same it's an easy swapt to put over. the trick is finding the rearend that fits and is the same width. with mine it went from the stock 8 open diff with 3.4's to a 3.89 spool in the 9 inch