I think it would be hard for a dual jet to keep up with a 2GC unless you just ran it on the jets alone and maybe trimmed the outer ring on the booster. Some of the 2gc's flowed pretty good. Those are the ones that the circle track guys look for. I'll bet it is easier to find a dualjet than a large 2GC. This is just my opimions. Ive always read that the dualjet cfm was in the 325 to 350 zone. I think that is where the smaller 2GC's start at and just get bigger fron there.
It would be somewhat easy to make an adaptor for a dualjet to fit a 4 bbl manifold but I dont think that one is commercially available. Of course there is always the stock intake (Chevy 305). I guess a stock dualjet would work fine up to a certain rpm t hen it would run out of cfm's. What kind of rpms are we talking about here? How many cubic inches? now if you could fit the 2gc's butterflys in the dualjet..........HHMMMM........I dont know, something to look into. Ive got a couple dualj's. Hopefully someone on here is more kowledgeable thanme on this subject