Slant 6 MPG Upgrades?

K I S S principle convert to either the Mopar ecu or HEI, plop on a super six, tune/tweak it out and call it good. I am so sick of electronics, and falling behind ever "current" ways, having to spend the $$ to keep my scanner updated for my daily work, there is much to be appreciated with being able to make changes with a timing light, distributor wrench, vacuum gauge and screwdriver vs flashing a computer, and such. They proved in the 70s that you could get great mileage from these engines, with none of Today's complicated BS,
I had a B body with a V8 that would get mid 20s if I drove it right, in the mid to late 80s... I have a different B body currently that does the same. A lot of today's vehicles with all the extra (unnecessary) electronics still don't.