Thinking about my Accent (Which in my opinion is an underachiever) got me to thinking about overachievers, It got me to thinking about cars/trucks that are overachievers for what would be expected for such a combo. The following figures are with just prudent driving (No Jack Rabbit Starts and No "charging" the redlight) and no extreme FE techniques.
: a psychological condition or a relationship in which a person is controlled or manipulated by another who is affected with a pathological condition (as an addiction to alcohol or heroin) ; broadly : dependence on the needs of or control by another
You only got 19 in your 74 Chevy? I had a 74 Chevy C10 4x2 with a 4bbl, TH350, and and air conditioner that thought it was a freezer (it would frost up the windows if given the opportunity). The only real mods I had done to it was I switched the points out for an electronic ignition out of a 75 Chevy van, and I put platinum plugs in it. I got mid to upper 20's in that truck with the cruise set on 60.
EDIT: Re-reading your original post I figured it out. I had a small block 350, and I had a lockup torque converter. My tranny had went out, and I had replaced it with a TH350 from an early 80's C10 with a lockup converter.