To date, in 50 plus years of working on carburetors and learning lessons; my most expensive lesson was a Weber two-barrel IDA that even the so-called Weber guru's could not make to function as well as a $5. swap meet flattop Ford (Autolite) 2-barrel. This lesson cost me almost $2500. several years ago when we were sponsering one of the dirt-track 4-cylinder race cars. Was supposed to be the "hot" set-up.
Lots of vintage carbs that will work well on a 250.
For a 250 CID Chevrolet, I would personally look at a Zenith from a GMC 248, one of the aftermarket Strombergs, or a Carter YF from a 240 CID Ford if the idea was a single barrel.
For a two-barrel (if a good two-barrel manifold exists, NEVER with a 2->1 adapter), a Carter WCD or WGD, a Rochester 2GC, or a Stromberg WW.
Others may have other choices.
And if I mis-read your post, and you are looking for a carb for a 235, difficult to beat the Carter YF (pick the correct one for your year), as Carter designed several specifically for the 235.
Jon.
