for what it's worth from everything Ive read you dont need an airgap, the current Preformer RPM works just as well and offers more clearance. I would add a spacer between the carb and intake a phenolic spacer (keeps the carb insulated from heat). As for a carb, Quickfuel VS 750
my two cents
interesting read
https://www.hotrod.com/articles/hrdp...pm-vs-air-gap/