I’m just finishing up a motor/trans swap (416 LS3 stroker/4L80E), and will need a bigger rear end to stand up to the power. I’m wondering if there is an easy swap that fits (similar width and bolt pattern). Maybe a 9” from a 70’s Mustang or a Dana 60? I’m not too worried about cutting off and welding on brackets, but I’d like to avoid narrowing or retubing. Any suggestions would be appreciated.

Unless you have a real sloppy gear, 2.7X - 2.9X, I think you'll find the stock 8.2 pretty stout.

Also depends on what you're gonna use the car for.

I've heard they are pretty stout, but this motor will push 600 hp and 550 ft-lbs. I feel like that's asking a lot from a 10 bolt.

Someone correct me if wrong but the 70 and up rears are stronger but they are longer in the snout by 1" and you have to shorten the driveshaft, I believe there is info here if you look up your year. The 10 bolt 8.2 is really only good for about 350hp depending on how hard you're going to dump the clutch, the latter 8.5 is better but if you're to beat the hell out of it Currie makes a bolt in 9"

A GM 8.5 will be fine
I will also sell my 12 bolt posi with 3.73, will bolt right in.
Im building a dana 60 for my car

If you don’t mind shelling out some cash, go to Moser. They sell me 12 bolt or ford 9” ready to bolt in. You can pick the ratio

1972-1979 V8 Novas and their GM cousins (Apollo, Omega, Ventura, Seville) came with an 8.5" that bolts in without moving the perches. With discs, it's the same width as the original with drums. All I changed was the u-joint and shortened the driveshaft. Held up fine behind the 455/400 (275s but not slicks). Many people run them as-is deep into the 11s on slicks even with a manual. If it dips into the 10s I'd recommend a girdle cover, and fully welding the axle tubes. Faster than 10s, you should probably switch to a 12 bolt or 9".