A friend of mine who used to be on here blew the hell out of his 7.5" when he had 33s. He was 2wd, 3.0L, 3.73 gears, and a manual transmission. The spider gears practically disintegrated when he was just taking a right turn.
You don't HAVE to upgrade your axle, but an 8.8" would be a pretty good idea anyways. You should be able to find one with 4.10 gears pretty easily, or you could go for an explorer one and get disc brakes at the same time!