When a builder continues to push the factory block beyond its ability, it might be time for a billet block. Take for example Scheid Diesel’s billet Cummins. The inline-six has a displacement of 6.7 L (391 ci) and is predominately used for Pro-stock tractor pulling. The model photographed below runs a Wagler head and produces 3,200-3,300 horsepower on 140 psi of boost. Of course quality and performance on this level doesn’t come cheap. Scheid Diesel sells the engine for $37,997.