Chevy Sleeper

You might recall the "hemi ban" from the late 60's or early 70's. Both MoPar and Ford had viable hemi race engines, and as a result were shutting the GM cars out of "Victory Lane".
While GM did, in fact, develop a Hemi head engine, there were a number of issues, not the least of which were patent infringements and reliability concerns. As a result, NASCAR banned hemispherical head engines. When Dodge came back into the fold last time around, the were forced to design a new cylinder head that was much closer to the GM/Chevy design head, than that of an LA or Magnum small block.

Just another of those little things that NASCAR has done to support one of it's benefactors.