Simple rules for the frames.
Never have an original rechromed. It will rapidly start rusting under the chrome. Actually most shops wont even try.
Spend the bucks for a never rusted frame from a dry area. Look inside if there is any rust then it is not an candidate. You are going to spend some serious cash getting this plated, dont skimp.
Some people have drilled drain holes at the bottom of the frame just to be sure the plating chemicals are flushed out. Some have put waxes inside to prevent rusting. I do not know what actually works over long term.
Originally the frame would have been plated with a dull nickel plate. Then just the front and sort of the edges would be buffed out. Then the front an side edges were masked off and the rest sprayed with a satin black.
Unlike the closed cars, the windshield slides on the sides were chrome plated, not just nickel.