Are you only changing the heads but leaving the cam, carb and shortblock the same? Looks like you were around 600 hp on the Moroso slide rule before since that is what it takes to push 3000 lbs to 9.8 @ 137. I'd think those heads would pick up 100 hp even with the same cam and carb so that puts you at 9.30 @ 145. But who knows, at some point another cork shows up in the system. The cork could be the cam or the exhaust or the carb. You'll just have to get it back together and see how she runs. The heads look good, they should support more than 800 hp if everything else is up to the task.

Depending on how much money is in the budget you might consider a different cam. Talk to Dwayne about what type of lobes would work with your existing valve train but could pick up some power for you. I don't think a 284/284 single pattern grind is what I'd be using with those heads but see what Dwayne has to say.