Harry in Ky

I have an S10 Blazer, '02 4WD. I have rear end problems again. It's been gone through twice in maybe 20,000 miles and is down again. Truck gets pretty rough duty and carries a lot of weight. Place working on it claims to be well experienced in rear ends and of course says it's not their work at fault here. Maybe it's just the weight I carry, maybe something wrong with the housing, maybe maybe maybe. I know less than they do, that's why they're doing it.
I'm not sure i buy the "too much weight" theory because I also have a older S10 pickup that carried the same weight for years before I got the Blazer It's never had any rear end problems. In fact, it's back in service again with the Blazer up on blocks. It has many more miles and still going strong.
Anyway, for lack of other ideas, I'm considering swapping the entire rear end for one from a 1/2 ton pickup. A quick internet search brought up one from a Silverado (not sure of the year) but it was listed as having 3:42 gears which is what I need to match. I can expect the usual cutting, welding, modifying spring perches, brackets, etc, driveline yokes, brakes and all that. Any other issues that might change my mind?