Driver for mileage

Longgone, I think the 2 inch would actually be better than my 2-1/4 suggestion.

MOPEkidD-3, it is possible, but the 7,000 ft. Alt. is a problem I believe. The other problem is the short drive you do. The car never warms up and gets into it's grove, so to speak.
I'd run through the upgrades I listed to longgone and look into this further. Carb tuning is a major issue for everything.

OH, I would not build a engine for mileage. Even more so with a 318 to start with in the engine bay now.