I remember back in the late 1940s through the early 1960s, the oil pan could be removed to allow ring replacement on some cars and this couldn’t be done on other cars. I know that on Studebaker 6 cylinder engines from 1947 through 1952 the pan couldn’t be removed without pulling the engine. On the other hand, the 6 cylinder Chevrolet engines through 1960 the pan could be removed by dropping the tie rods and jacking up the engine. I think that the old Ford flathead V-8 engines would allow the pan to be removed without pulling the engine.
I learned the hard way the difference between a ring and valve job and a proper overhaul. I bought a 1955 Pontiac in 1962 from a Rambler dealer whose service department had overhauled the engine. It was a bad purchase. The cylinder walls had be honed, the ridge removed at the top of the cylinder and the valves ground. The car didn’t use oil. However, on the 1955 Pontiac the oil filter was an option and the one I bought didn’t have that option. Apparently, there was sludge in the engine and the sludge would get into the studs on which the stamped steel rocker arms were mounted. The engine would then chirp. I had the studs pulled and cleaned out. I replaced the hydraulic valve lifters as they had not been replaced. Even so, the chirp would return when I drove on a trip of 200 miles or more. I never did solve the problem.
Had the job been done properly, the engine would have been pulled out the chassis, stripped down and all oil passages cleared out. The lifters would have been replaced. The crankshaft would have been miked and the throws reground if necessary. The camshaft would have been examined for excessive wear and the timing chain replaced. At any rate, I did learn the expensive way the difference between a proper rebuild and a “ring and valve job” which really means a sloppy patch.