[countrypuppy4865]

Upon my own research, I have gathered that the 405hp engine for GT was previously rated the same as the regular LS1, but the 405hp version has only one casting number for the head. This casting number is not the same as any other LS1 engine. Therefore this makes this combo different than the others. Is there 90hp more in this head? Absolutely not. However, it is listed with only one casting number for the head.