Intake manifold fitment

One thing related to all builds & brands, even with the "correct" manifold, is that you can't be sure if the next manifold you get will "fit" due to block decking, head milling or intake milling. Sometimes you'll see the intake bolt holes ovaled-out to get the intake bolts to line up with the heads. But doing that does not line up the ports! The results are mismatched ports and performance not meeting full potential.

For starters, you can lay the new intake on the long block without a gasket and see if the bolt holes line up. If they line up well, it means that you'll have to mill the intake or the intake side of the heads the thickness of the compressed thickness of the gasket to be used so it does line up in final assembly. (Using supplied end rail gaskets complicates things because they can hold the intake up. I usually use silicone there for final assembly.)