Hi, this is rockrollmanny. I have a 1968 Firebird, running a pontiac (poncho) 455 (.30 over). I purchased all my engine parts from Jim Butler Performance Pontiac, 6x heads prepared by Jim Butler. Dyno @ 318 HP at the wheels. If you are a pontiac person, I recommend "Pontiac High Performance" magazine. Too the "National Firebird & Trans Am Club". What is your goal for the poncho motor, street/strip, all out racing ? Street use, keep compression no higher than 9.7 (91-92 octane gaso). Check out the following web sites, Jim Butler Pontiac, Rock&Roll Engineering , this are two that come to mind. There are more and they are all good. It just depends on philosphies and how they approach poncho horsepower. Check them out. Hope this helps you out Scooter, Good Luck! RockRoll Manny