I have a Savage SS K4.6. The only things I've needed to upgrade so far after over 2 gallons are the clutch shoes, went to the Nova aluminum shoes and Mugen 1.0 springs. Upgraded the stock 39 tooth gear in the transmission to the new heavy duty hardened steel clutch holder design. Made a center skid plate from a peice of scrap polycarbonate from work after coming down on a rock and bending the brake discs ending my day running it. Added the safety engine stop button. Will probably upgrade the diff cups to aluminum sooner or later and looking at a set of offset wheels and maybe a set for the street too.