A Rochester 2G would be a good carb if you want to run 2 bbl. It's what the 231's predacessor, the 225 used. Depends on what vintage 231 you have as to what adapter would be needed. If you have a '79 or newer 231, you could run the Edelbrock Performer intake and Edelbrock Q-Jet 4 bbl carb #1904 as I am and have the best off-road carb made.
What is the CFM of the Q-Jet #1904? I've read that there was a specific Q-jet made for the 231 which is smaller than the Q-jets made for V8s, but I did'nt see any CFM ratings. I have a 84-85 3.8 liter if that makes a difference.
The cfm of the 1904 Edelbrock Q-Jet is 795. You will never utilize that much from it with your 231 due to it's design. You could search out the Rochecter Q-Jet that came on the turbo-231's and the 252 from 1980 and prior, ('81 and newer Q-Jets were computer-controlled), but the 1904 Edelbrock works equally well on both my '66 Jeepster Commando with Buick 252/4.1L V-6 as it does on my Buick 350 V-8 powered '70 Wagoneer.