[elhigh]

Definitely put the older heavy flywheel back on. That extra mass absorbs a lot of your quick power output when you're dragging and that's when you don't want a heavy flywheel. But when you're looking for max mpg, more rotating mass is better - it makes it easier for the engine to coast through its dead spots in the power delivery cycle, and delivers smoother power pulses to the drivetrain. In FE, smooth is good.

Why stop at 175/65 tires? Keep looking and try to find 70's or, be still my heart, 75's. I don't think anyone is making them, or else I'd convert my truck to tall, skinny 15's tomorrow. You may find some luck in this arena searching among the VW sites - those old 15" wheels were like pizza cutters.