A 235 ci engine requires 139 cfm at 2400 rpm to run at top efficiency ( carb wide open ). The smaller carb might give better throttle response due to higher air velocity, but at higher rpm could restrict some cfm. I would use the one that doesn't leak, but if you can make both run with little to no money, try them both and report back with your finding.
There are a lot of charts and calculators for finding cfm of engines, yours will have an efficiency in low 70% range if that due to the terrible cylinder head port design. The cfm result is maximum amount of volume for a given rpm, normal driving requires much less.
