Karl, you think 40's will fit under 10"? My buddy has 40's on his, but he's at like 12-12.5" of lift. He also had 4.56's in his and ditched them for his factory 3.73's believe it or not. I think he said it would have been more ideal with a 4.10 in there, but he had the 3.73's laying around and liked them better than the 4.56's. Just food for thought. Guess it depends what you're doing with it too.

 

Check with Top Gun Customs about stacking another 2 inches onto their lift kit. They might be able to help you, I'm gonna guess they'll probably discourage you from attempting it. Their kit should help compensate for the caster and driveshaft angles and length, then the extra 2 inches will throw it out of wack again. But hey, it's your truck, just keep it under control so you don't get anyone hurt.

 

My inputs are in red.

 

I am one of those guys with 35's and a leveling kit, but to go to a 37" tire you need a 6" lift. Two of my good buddies both had 05+ cc/sb trucks with 6" lifts and 37's and both rubbed. Both were on aftermarket wheels too, different widths/offsets. One truck rubbed the inner liner when turning, and the other rubbed going over bumps. Both required trimming in different areas. A 37" tire is not only 2" taller than a 35" tire. For whatever reason, 37 from a 35 is a bigger jump.