Craig for what it may be worth, I agree with Jerry on this and also with Mike when he says "if you are thinking you are going to get a lot of power after modifying things, you are going to be disappointed."
A friend of mine about 50 years ago did this. I can't recall the brand of manifold he bought but it was considered the best one at the time. It "worked" but it never seemed to work properly. He tried all kind of different carburetors including Carters made for a Jeep, Rochesters of all sorts, smaller jets, larger jets, etc, etc. This was at a time when you could buy brand new Carter carburetors from any parts store. He fiddled with it for over a year...and I should add this fellow worked for a Chevy service dept. After all his efforts he admitted it was wasted time and money, went back to the stock manifold and got a Carter YF one bbl. Here are what I remember some of his complaints as being: linkage challenges, vacuum challenges, worse gas mileage, only slightly better performance, constantly ran rich and could never manage to heat the manifold properly, spitting/coughing, could not make it run lean at idle and at highway speed it would not run smoothly (it was in a 1959 El Camino, by the way).
Here is more/less how he told me the manager of the shop explained it to him: imagine your manifold as a smooth lake and first think about the stock manifold. You toss in a single rock and it makes ripples and all your cylinders suck vapor out of that single ripple configuration. Okay, not perfect because obviously the central two cylinders are favored due to their proximity to the center but now imagine this...you toss in that first rock to the left of the center point and another rock over to the right of that center point as quick as you can. Now what happens? The ripples intersect and that intersection point now produces interference and turbulence. What does that do for you? Well, it is open for debate but the GM engineers knew you would avoid that intersection turbulence with 3 small carburetors (what Jerry is talking about and what happened with the Corvette). In my opinion a 1960 235 works really well with a Carter YF3211S carburetor. It is an auto-choke, but personally I prefer that.
Good luck if you choose to go the twin carburetor direction. I think I'd talk to Jon H (CarbKing) about it.
