Trying to help out a fellow HAMBer here- Buick had the rear signal lights in the trunk emblem as far as I can find in 39, 40, and 41 only. Oldsmobile also possibly. They used a 90-degree bulb socket with twist connections on both sides. In my research, these items are really rare. I had a spare set of the sockets to share, but not the wiring connectors. Since they not to be found, my idea is to make some using either a gutted bulb socket and POM plastic or solid Bakelite rod. maybe a different approach or plastic?
Had the same issue and went to my local chain parts store and bought a dual element socket for 1157 lamps. Cut the old socket out and soldered a ground wire to the replacement socket on the outside. You can choose which of the two wires gives the brightness you want, and just safe the second wire on the 1157 off. Works great for my car. The replacement sockets snap in, so once I installed it I bent some of the tabs over to ensure it was going to be permanent and not pop out.
I'm thinking you could use a chunk of nylon or Delrin, a replacement pigtail set, and a piece of coat hanger wire. Use a small hole saw without the pilot bit to cut a slug out of the plastic, drill the slug to wire size, put a long machine screw thru it, chuck the screw in a drill, use file to "turn" it to correct OD, counter bore it to spring size & depth, drill sides for locating pins, force in short lengths of coat hanger wire for the pins, and finally insert the contact wire and spring.
This is the option I am going to do, and I ordered a stick of 5/8" Delrin rod. Machine the rod as you described and press it into a thin brass sleeve. I am going to use S/S tig wire rather than the coat hanger. The HAMBer I sent the sockets to is going with original cloth wire, so I wanted something that looks original.
Not pretty, but functional and hidden up in the socket. 5/8 " Delrin rod and hollowed out 1156 socket.
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