1965 273 2 bbl engine.

Most offenhouser intakes have both angles for intake attaching. The 66 and later manifolds are counterbored for the 66 and up mounting bolts wile the casting has the 64-65 angle. All you have to do is use a larger than the counterbore hardened washer and the right length 5/16-18 bolt. The correct intake would be D4B Edelbrock the correct 65 factory 4 barrel intake, and Offenhouser made Intakes for the 64 to 65 273. There are only 2 intake port sizes, small (273 and 318 ) and large (340 and 360). All 64-67 273's are solid lifter cams and the same as any other small block Mopar. The 500 cfm Edelbrock 4 barrel will fit the Factory 4 barrel manifold without modifications. I doubt Magnum heads will fit on a 273 without Intake notches in the block due to the small piston bore.