Do you want it done right or just pretty?
From the factory they were ground flat on the front, copper, buff front face, dull nickel plate, buff front face, chrome buff front face.
Note the dull nickel plate was what was used back then. Today they use a bright nickel at many shops which would make the back side not look correct. The back side should look like the dull side of aluminum foil and have mill scale.
Your problem is getting the back side looking properly. You need the dull nickel for the proper effect. So when you look for a shop ask if they dull nickel tank and can they chrome plate buffed dull nickel.