I'm debating on what motor to build for my '80 GMC. It will be entered in local mud races, but also driven on the street once in a while and alot off road. My options are a .060 over 427, std. steel crank, domed Keith Black pistons, and open chamber heads. Or, a .060 over 454 (468 ci) with the cast crank, flat top pistons and closed chamber heads. The truck will have 40" tires, 4.56 gears and a 4spd/205. Which motor sounds like the best application?