My 390 is really fuelish, too. You’re right, gas mileage wasn’t a concern until the 70s.
Yes that first arab oil embargo in 73 really changed things. All of a sudden most every American knew where “Saudi Arabia” was on the map.
I sat next to a guy at work who was probably 6-4, 270 pounds.
He panicked and sold his Buick 225 for far below value and bought a Vega, soon to realize his terrible mistake.