From what I've read on 1936-1942 Proof sets, it's a bad idea to try to just keep them stored in their original packaging. Yeah, it's very cool and historic, but not very good for the coins in the long run. That packaging was not meant to last for a hundred years. It was just convenient packaging for the Mint to get the Proof coins in reasonable safe condition to their customers. If you're so concerned about the packaging and planning on selling, then I would present the set to one of the auction houses, like Heritage and see what they think. Otherwise, I might contact PCGS/NGC directly and see how they would handle such a set. Maybe you can send it to them directly (and very carefully as you don't want the coins banging together) and they'll remove the coins and put them in a nice single Proof set holder (I did this some time ago for a 1942 and 1950 Proof set which I no longer own).