EXHAUST: We ordered a MagnaFlow 2 1/2" stainless system from Summit
http://www.summitracing.com/parts/MPE-16643/ for a 1972 Chevy C10. We knew it would need some modifications to go over the rearend with the air ride and connect to the LS3 but it gave us a nice base to start with. I got some stainless flanges from Yoshi fab
http://yoshifab.com/store/ to hook up to the LS3 manifolds.