I own a 2000 35 Fountain Lightning with carburated 500 HP's without silent choice/has tall gill exhaust. I was told it has a 600 lift cam which cyclinder heads would be the best for replacement/ Dart Iron Eagle/308 intake runners or should i go bigger.

i would think the iron heads a good choice , even the dart pro one counterpart a great choice , i run 345 on a 598 with a relative small cam , and have been told that they might be a little too big , although i sure feel them come on at 3200 and above !

AFR 315 on that bottom end should get you around 610-625 hp but the Dart pro one is also a good choice.