New old '66 Barracuda

eholster,

I have two 1965 273 V-8 engines and both have the "more vertical" tapped holes for the intake manifold (7/16 coarse thread I recall). I measured the holes as ~16 deg off vertical. Later engines changed to the ~45 deg off vertical holes, until Magnum engines which have vertical holes. I recall they also went to a bigger bolt (1/2" coarse?). I think it was only '64 & '65 LA engines that had the 16 deg holes, but many posts about that.

If your holes are ~45 deg off vertical (perpendicular to intake surface), you probably have later heads, though I have heard of people drilling and tapping new holes. I mounted a later intake alum manifold on my heads by countersinking the manifold holes to fit a flat-head screw, as others have.