That's a 25-35 cfm difference in the meat of the curve .300-.500" probably at least a 50 hp difference on a decent engine. The SM aren't to bad for the level of head they are, like to see more .300" on them though, still probably make a decent 450-475 hp engine depending on the build.
Ya i was wondering how much of a difference that cfm would make but i thought it was close enough should have done more research . at least the heads are still bare could always spend more money and have them worked over i guess