If you stick with the Eaton get it ported. You are not going to find a better combo then a 3.1/6lb. I was putting down insane numbers on a safe tune. Best times/numbers I've seen on Eaton cars seem to be ones with larger lowers. 3.1/6lb with some cooling mods, Maf, and a BAP and you should be in the 530rwhp/545rwtq range.