how do you find out if i have a lt1 motor i have a 72 vette motor in the truck i ran the casting number by the tranny bell housing and it is a 350 4 bolt main i took the valve covers off yesterday and found numbers on it on the top right is a gm stamp and below that is a 21 then there is a casting number 4626240 then on the side of that there is a l6 and there is another number 11 at the top by the casting number.

 

The LT-1 had solid lifters, Holley carb, and aluminum manifold, aluminum finned valve covers, etc.