Anyone know if there's an easy way to buy a complete 11.5" with 4.10's. I need some lower gears and have a 10.5". I figure it makes more sense to just swap in a 11.5 than to spend lots of money putting in gears in a 10.5" (I don't know how to set up gears myself and would not risk learning it on a $1000+ rear end).

I would guess that everything else would match up (driveshaft length and brakes) but can definitely check.