Is there a carter carb that will fit this wider bolt spacing?
The short answer is: YES
The long answer:
The size 2 (2 11/16 c-c mounting) was used on the 216, and early 235's.
The size 3 (2 15/16 c-c mounting) was used on 235's, 250's, 261's, and 292's. Just because a carburetor will bolt up does not mean it will work. The internal venturi size will vary, based on the displacement. Very first thing to do is determine EXACT engine size and year. Then you can look for a carburetor that will function well with the engine.
Jon.