This maybe dating myself but way back when. (Like "Once upon a time").

Before they ever had the "Fat Book" and other aftermarket companies, we made our own custom parts. I had an old '70 XL and didn't like the stock carb either. I went to the local foreign auto wrecking yard and got an SU carb off of an English Ford. Took a little work to set it up but it worked great.
I think, the CV40 would be much better then the S&S. The S&S would be too big and the jetting would be a major PIA. I'm not sure but I think there is a kit to mount the CV40 to an XL. CD would know for sure. Have fun and be careful of the "Sportster Knee".
