As stated it will depend on the desired application for the engine in question. Greg's outline is pretty much what we follow. Hard to beat the Edelbrocks for value. I have no first hand experience with the 440 source heads but I would think they would be pretty hard to beat as well for anything in the 600-700hp range. Provided they get a good bill of health. If it is primarily a street car I think I would want to keep the port cross section smaller to make it a more street friendly set up, especially in a heavy car. I had very good luck with Indy SR's in my Belvedere. It was 3770lbs with a 451 and SR's with the std port size and the car went 10.50's on pump gas. Worked very well for me..