Let's see.
I can replace my model B with a Carter. Probably have to change/modify gas line, vacuum line, throttle linkage, choke linkage, air cleaner. Plus cost and hassle to buy and ship "new" carb from (possibly unreliable) eBay seller. The "new" carb would probably have to be rebuilt.
Or I can simply put a kit in my existing model B.
I can imagine which option would give me the headache!