In my opinion the YF3211S was one of the best carburetors made for the 235...but if you're married to the idea of a manual choke the only option you have with the 3211S is to use one of the aftermarket adapters (turn auto into manual). Those adapters work, but honestly speaking they are not my first choice. The YF3211S came out in 1957 and it did have the central shaft air cleaner retaining bolt. With the 235 made from 1959 forward, you need to understand things changed. This might mean using a carburetor made for 1956 and older engines won't work quite as well. What changed? Specifically smog and air pollution were getting more attention and GM took steps to make the 235 more efficient. They adopted a new camshaft which produces more torque at lower rpms...thus using less fuel and particularly helping make the engine more efficient in heavy traffic situations (think bumper to bumper). The 1956/57 camshaft makes the 235 produce torque of 210 but at 2400 rpm. The 1959 cam makes it produce 217 at 2000 rpm...more or less a return to the 1953/54 Corvette numbers of 223 at 2000. If you're using a different camshaft, then all bets are off on this idea, however. If you study the YF3211S, you'll see the metering rods were designed to make it run leaner than the 2100S. The 3211S returned to a 2 step metering rod (don't really know why), and both the economy position and the power position are larger than the 2100S...meaning they take up more room in the main jet which was the same size in both. My theory was that the Carter folks (also pressured with lowering emissions) returned to the 2 step rod so that the 3211S would remain in the economy mode longer...thus reducing fuel consumption and keeping the 235 in that zone longer. If it were me, I would leave the manual choke mechanism in place and have an auto-choke...in other words just let the manual choke exist for appearance sake. If you're using a later model 235 in your AD pickup, you've abandoned the idea of keeping it 100% original anyway. Around 1964 or 1965 I was looking at the same decision. A mechanic in the village where we lived told me "use the auto-choke. Those things are going to do their job better than you and that's one thing you don't have to worry about."
I am constantly watching for new old stock (NOS) or close to NOS Carter carburetors. They're getting harder and harder to find, however and very expensive. I have a very nice YF3211S at this time but no YF2100S models.
