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.