273 v8 intake question..
The best and easiest way to go is to install a four barrel aftermarket intake manifold for the early 273. The difference between the early 1964 - 65 and the later ones are the bolt angle on the intake. They were different but you can use them if the washer is made with an angel too. But it's better to use the right stuff from the beginning.
Supplier is Edelbrock, Weiand, Offenhauser. You can find then om Ebay or at different speed shops.