I'll add something else, since it's easier to just answer the darn question than to make the guy do a bunch of searches for topics.
I used a really good 2-barrel carburetor on my 235 that might work for you. I got it from Langdon's Stovebolt, and it was a Holley-Webber carb. It had two bowls and took two jets, one a primary and one a secondary, and had a progressive linkage. The carb was real cheap, as was the adapter and linkage kit. I suggest buying everything Langdon offers since it's all engineered to work together and it works really well.
Your only task is to get the right jets. Those jets are not sold by Holley anymore but I may have a few if you end up going this route. What you'll want to do is solder the hole of the brass jet closed and then use a precision drill bit to drill your own sized hole until you get your carb about the right air/fuel mixture, which you can see from looking at your exhaust pipe emissions and spark plugs.
I'm sorry but I don't remember what size I started out with. But I want to say it was about like a standard #52 Holley jet on the primary and maybe a #58 secondary. But then again I was at a mile altitude.
The carb made a LOT more torque, and I got an extra 600 rpm on the top end too. So it ran very well.
