Shifter threads

You are saying that the chrome plating made the threads smaller? I don't see how that's possible. Typically they get a few .0001" bigger from the plating. Still should be well within tolerances for SAE threads like that.

What does the O.D. measure?
I have had this happen before with chrome platers.....the handle got left in the tank too long when the chrome was stripped. I have repaired lots of damaged threads by machining the handle down, then drilling a 3/8 -24 bolt out and pressing it on like a reverse heli-coil. Tig weld the end to keep it from coming loose. Have always done this before chrome though...