never ever ever ever buy a thumpr ever! no matter what the use is! the xe268 is a fun cam for my vortec 355 could bennifit from a 1800 or equivilent stall but the stock one doesnt have any problems burning the tires off!! I have a limited slip posi 3.73 for my el camino and it lays to black strips down everywhere it goes! whats the combustion chamber size of the heads? compression ratio is very important!