If I use 66 or later heads I will have to notch the cylinders for intake valve clearance? Or do I only have to do this only if I use aftermarket larger valves? Also can I mill the heads to get the compression back to stock specs? Sorry for all the questions but I'm new to the smallblocks and pretty ignorant to the parts swapping. Thank you for all the info. Litz
66 or later 318 heads only. The 340 and 360 heads have larger combustion chambers and vales that aren't friendly with the small bore of the 273. They also have larger ports that also don't match up with the 273 intake and exhaust ports.