Carb for super six conversion
Is there no way to make it work?
Really, there isn't. A feedback carb will not provide good performance, economy, or driveability. You could probably cobble together a feedback system—some of the '81-'87 Slant-6s had it, notably in California—but even when all parts of the system are present they don't run very well. The priority there was squeaking, at absolute minimum cost, past the new-vehicle emissions certification tests so they could be offered for first sale. Everything else (performance, economy, driveability, fixability) was out the window.
Do you know where I can get a good carb that doesn’t need a rebuild?
It's grown much more difficult than it used to be. "Remanufactured" carburetors tend to be a waste of money (junk), and the internet is flooded with cheap and nasty Chinese knockoff BBDs (such as the one RustyRatRod linked) that I would not let anywhere near my car for safety reasons (don't feel like watching my car burn down, especially not if it's in my garage at the time).
From time to time suitable carbs go by on eBay. Such as
this one. Save yourself a lot of hassle and go ahead and get the № 1232
Electric choke kit right off the bat.