Fuel Mileage on your Hemi swap?

Late to the party, but my 67 with an 06 5.7 with a moderately aggressive cam, viper T56, and 3.55 gears seems to get around 20-25 on the highway if my Megasquirt is to be believed. My odometer is semi dead as it's been my eternal project to get my factory gauge running with the speed sensor on the modem transmission, so don't have the most accurate values, but it's been pretty consistent. Hoping to tune it up a couple more now that I have knock sensors, but haven't really gone after it. My commute might be changing though, so that project might be going up in priority.