Smallblock efficiency or How to have your cake and eat it too

Hmmm... Subscribed.
I'll add my 2 cents.
I have a roller-cammed (1990) 360 that i've rebuilt with 9.7-ish compression. Lunati voodoo cam. With MSD 6A as well.
The absolute best mileage I got when I used the 650 AVS was 17.5-17.7mpg hwy, 12-ish city.
Then I stuck on the 750 Street Demon, HWY mileage dropped ever-so-slightly to around 16.9 with about 17.3 being best.
But the city mileage with S/Demon is what I call... meh. best is 10mpg with 8-9 mpg avg mostly. But it's so much more fun!
I have an A999 converted to non-lockup with 3.21 rear gears. (yeah I know, if I kept the lock-up the mileage would've been better)
To me the biggest mileage factors is tuning (I used AFR gauge) and RPM's.
I used to own a 1988 Dodge ram W150 with 4.10 gears and 33 inch tires. 360/A727 4X4, on hwy at 65mph running about 3200 RPM I got 11 mpg. I think the barn-like aerodynamics and being about 4800lb has alot to do with it. (I still miss that truck ~RIP)

*Edit: BTW I'm at 4500 ft elevation, I definitely have to run 91 octane premium at the minimum