My 23 got fantastic milage. 350 Vortec, marine cam, TH350, 3.00 gears, 30 inch tire in back. Normally got 20-23 around town and one time on a trip it got 30 mpg at one point. At 60-65 I was just slightly off idle. It was also very light and had no wind resistance because of being so low.

My 27 has a 331 Ford and 4.30 gears with no overdrive. I don't even want to know what the milage is on this one.

Don