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Another intelligent answer, spend more money!

What 65Vart said. Better off tracking down a intake to fit easy.

Otherwise, what he said again. Hog out the bolt hole to the new angle, spot face weld the rest shut or use a washer to cover the hole up.

The issue of oil coming up through the bolt hole is very possible. You can stop it with lots of telfon tape. Fill the hole with sealent. Then theres the bolts new angle, the head will not sit flush with the intake. Some brain said to me once, have wedges made so it sits right. Perhaps he never tried to have that done, perhaps he knew somebody and had it done easy.
I'd rather spend a little more, than to mickey mouse something. I'm not even sure it would cost much more to use a later setup. What does a '64-5 only 273 only 4bbl intake cost?? $125? 150? I've seen the '68-up intakes for as little as $50.00 for some models. With the difference, you could get a later set of heads along with the manifold and be able to use the easier to find intake gaskets. But hey, if your engine is working fine and you just want to add a 4bbl intake, go for it....hog out the holes, use a tube of RTV to seal it, and boogie on down the road. It's just not the choice I would make, that's all.
Been there, done that, and wasn't happy with the results.
Mark