66 Barracuda 273 Intake Manifold options?

Try running a bottoming tap in the intake holes, then screw the bolts in to see if the distance between the bottom of the bolts & the top of the intake leave enough room to compress the housing gasket. Just a shot in the dark for you.
Thanks, thats one area I admittedly have been neglecting. I may go get one of those bottom tap sets later today.