Daily Driver.. LA318 vs 360 Magnum

My milestone--and I realize things were different then, fuel for one........in about ??73 I swapped a 340 into my 70 RR which was a 440-6--complete with hemi gearbox and Dana 3.54. So a bit heavier and more friction than the "average bird." I did put headers on it, and ran, variously, the Thermoquad, and a couple different Holley spreadbore, which were new technology at that time. That ol thing would get 17.5 and I was NOT a "careful" driver as to fuel mileage.