Sagging rear end

[keanoknick]

wondering if i could run 38.5's on 20 inch wheels with an 8 inch lift on a 2008 f250. has anyone done it?

I run 38.5"s on 18" wheels, with an 05.
It shouldn't be a problem with your 08, the suspensions in the front are pretty much the same, you just have longer leaf springs in the rear.