I don’t think gayges were required to work. Only the fuel gauge works in my 57 and there are ni sending units for the oil pressure or water temp. Heaters were an option in 57 so you would not have to have one. Unless you are trying to perfectly replicate a car I would not sweat some of the small things. Just make the motor appear correct,i.e. intake carb and maybe the heads, put the 7 inch tires on it and come out and have fun. The 57 I am lucky enough to have is only period correct, other than a couple of safety features, because it sat from 71’ until I got it.