The Pontiac 400 Ram Air engines shared cylinder heads between applications, and understanding the head casting numbers is critical for verifying a Ram Air engine.

The Ram Air I and II heads used the standard round-exhaust-port casting. The Ram Air III introduced a new casting with improved exhaust ports. The Ram Air IV used a third casting — the largest exhaust ports in any production Pontiac head.

The head casting number is on the outside of the casting, and reference guides list every casting number with its corresponding application. A Ram Air IV engine with Ram Air III heads has been modified. An engine described as Ram Air IV should have the correct casting numbers in every major component.