Like I said, if the carb truly IS a Carter AFB, then it's a squarebore carb.
If the intake manifold is the stock intake for a 305 with 4-barrel carb, then it's a spreadbore.
There are no easily available Chevy squarebore intake manifolds that I'm aware of. Yeah, some were made, but for special applications.
And as I said, you can probably find an Edelbrock 2101 intake manifold pretty cheap. I found 6 of them in a quick search on eBay, with prices varying from $13 to $115 (stay away from that one. They sell brand new for $115.95 at Summit.)
If you don't want to do that, you can go to a local parts house that carries a few speed parts and buy spreadbore to squarebore adapter for about $20. I don't like them because they're aluminum and conduct heat to the carb real easily. But they will make the carb and manifold bolt up.
