I was watching this video in passing he mentions trying the Dominator on this engine, he stated for some reason the 3 times he's tried it on LS3 heads it loses power, but everything else sbc, bbc, cathedral ls's it's gain power.
I'm guessing it's got to do with something about the shape and or velocities of an LS3 head.
I think LS3 ports are generally to be considered on the larger size, kind of like Chev's version of the Cleveland.