65 273 Intake manifold

Looks like I made a mistake buying the manifold. Its a running car with the original engine. Just wanted to get rid of the troublesome 2 barrel.

Easy to tell, do the intake bolts use a 1/2" wrench or 9/16" wrench? 64 and 65 original heads use the 5/16 bolts and 1/2" wrench at the non standard angle.