I've come across some info that suggests that '63-64 273 intakes and heads are different than '65-68. Is there any? More performance,less-interchangeability?
64-65 heads & intakes use 5/16" attaching bolts that are at about 20 degrees from perpindicular to the intake surface. 66 and later use 3/8 intake bolts that are perpindicular to the intake surface. 64-67 have small wedge heart shaped combustion chambers (57cc), 68 and later 273 & 318 heads are basicly the same with open combustion chambers (62cc)& all have the same size valves & basicly the same size ports and will bolt on any 273-318-340-360 block. It's harder to get good compression with open chamber heads.