Initially, General Motors made seven different versions of the LS engine, and the majority of them had varying heads. The head names are indicated by the stamp on the valve cover that shows the three-digit head number.

The 243 heads were put on the LS6 engines. Initially, the heads were made for C5 Corvettes, used from 2001 to 2006. The LS6 was also used in some Camaros and Pontiac GTOs.

The 243 heads are cast out of aluminum alloy, and they feature larger intake and exhaust…