The key player in our build is this Gen III 5.3L aluminum crossbolted block, also referred to as an LM4 (PN 12566910 or 12571048). Originally designed for an '04 Chevy SSR, Trailblazer EXT, GMC Envoy XL, and Buick Rainiers, it shares almost all the attributes of its larger displacement cousins. Theoretically, due to the liner thickness, we could have bored it out to a 5.7L, but if we wanted that we would have just picked up an LS1. Besides, our Camaro originally came with a 327 so this displacement had a bit of nostalgia. The only machining done was a light "clean up" hone to the cylinders.