What tires size and rear gears do you have?
I run 4.10s with 2wd stock-sized tires (285/60R18), and I tow 7,000 lbs. realatively easily, but I don't line at your altitude..
Lower gears make a huge difference, even with a supercharger.
Lightning guys often put 4.10s in with stock wheels/tires, so if it helps a high-power 2WD truck, you can bet it'll help yours while you are towing.
If you have tall 4x4 tires, you can go even lower with the gears.
You won't run out of revs even with 4.56 gears and stock-sized tires, which at least one person on this site has done. And he's got a blower, too.