Well 66Step, I'd say you're doing pretty darn good with that mileage. I get about 11-12 on my '65 with 292/T5(also a .63 OD)/4.57 rear/long tube headers/4 bbl/HEI. I've tuned and dialed everything in to the best of my ability and can't get anywhere near even 13mpg. I'd be ecstatic if I were gettin' 16 mpg.
-David
