what combo = decent mileage+ power/torque

My 360 is getting 17-18 mpg around town and 21-22 on the hiway. Filled up yesterday and it was 21.5.

This is a 10.6:1 engine with a comp XE268H cam, dual plane intake, magnum heads, headers, 670 Holley Street Avenger. It's in a 68 Barracuda with an A833OD tranny and 3.55 gears. Turns just a little over 2000 rpm at 70 mph.