I'm not real sure on the 5.0 stuff but i know of several guys that have ran even 12.9x's @ 103ish mph,with around 260rwhp from a gt 4.6L! It takes good suspension equipment(drag stuff) good air, and 5000+ rpm clutch dumps on slicks! I'm in the same boat as you, I make more hp than them and just can't get it to the ground either
Leon