31 10.50 15 on stock rims and 4x4 blazer.
I'm not even sure you could get 10.5" wide tires to fit properly with 2" of lift.
as for fitting on his truck, i'd lean towards you guys knowing for sure (i haven't lifted my truck yet). i do know they would fit on the 1st gen's-without any lift (body or suspension). i was running 31's on my '84 before i lifted it. ok, they did rub, but only if i had the wheels cranked all the way and hit some bumps. but under normal driving, they were fine.
mine isnt 4x4. mine is 2wd. I have 3.5" lift by fabtech and 31x10.50 on 15" rims my front wheel sticks out 1.5 inches farther...still had to trim inner fender quite a bit...





