Here's a wild idea that might work.. Find some old VW enthusiasts.. Many bugs in the 70'sThere are a few books around. Haynes do a book on Weber carbs, but not vast amounts on the downdraft carbs. The Haynes Sud / Sprint manual has a few bits in it. There is a fair book on setting up the Dellorto DRLA downdraft carbs, which I can dig out the details if it would help. After that it is time to dig out the Alfa 33 workshop manuals, or even the Arna manuals.