If you are going to use one carb on a 235, then use a 235 carburetor. A single 216 Rochester B on a 235 will significantly limit the capability of the engine.

If you are going to use two carbs on a 235, then:

(1) Fill the threaded holes in the intake, redrill and retap for the smaller flange.

OR

(2) Slot the throttle body

(Opinion) the only reason for putting two carbs on the 235 is "eye candy". Slotting the throttle body is more like "eye xxxx" wink

Jon

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop