It looks like the same design philosophy as my Weiand 7503 4-barrel Poly intake. As said above, it's a single plane with a divider down the middle. It's a lot easier to cast than a dual plane intake.

I was probably still in college when the last competitive Offy intake was introduced. They are nowadays strictly nostalgia.

Rochester 2-barrel carbs are easy to find. They have two different bases. The larger bases are preferable as they have the same interior dimensions as a 500 Holley, but GM rated them 435 cfm. That's equivalent to 308 cfm in a four barrel.

The smaller base max carb size would be 390 cfm, as a four barrel it would be 275cfm.

The 1965 and earlier Pontiac 389s and smaller used a smaller center carb and two larger outboard carbs. The 1966 used three big base carbs, and gained power.

IMHO the best place for this particular intake would be in a cruiser or street rod. An Edelbrock Perf RPM and suitable carb would probably be 50hp above this one.
As this intake is low rise it may fit under a hood better, another thought.

To OP: Clean it up, take really good pictures and put it on Ebay. It may take a while to sell, but there is a buyer out there for that intake.

R.