I do volunteer historic railraod preservation work in the summers, and this same question comes up. (Hmm, the Johnson Bar on a steam locomotive has notches, making them sort of "index shifting" I hope this still counts as on topic!) We were contemplating restoration of a flat car built in the early 1920's which was a disaster of a design, heavily modified in the 1930's and again in the 40's. Each of the conversions can be considered historically correct.
I say don't sweat it, unless you are going to do something that can't be undone. Part of the fun is continuing to improve our toys as we learn more and the right stuff comes available!
Cheers from Dallas, TX, USA, Earth -
Clyde R.Putman