I believe stovebolt only carries one for the 1.5" It's a generic part, not specifically designed for this engine, but works reasonably well and allows you to orient the carb with the float bowl forward which, in my experience, makes a big difference in how the carb performs going around corners. FYI, this experience is based on using a weber 38/38. Also worth noting that the stovebolt is WAAAY cheaper than the clifford's part.
I haven't measured, but perhaps it could be bored out for the 1.75" intake. The holes are slotted on the adapter, so that's not a problem.