Does anyone reproduce the part that screws into the taillight housing on a '68 El Camino? I am looking for the piece that had the two spring-loaded prongs that make contact with the actual bulb. All I can find are the newer-style screw-in sockets.

Might give American Autowire a call.

These are used from at least 55 on up to (my 66 Elky has em) to I dunno.
They were not used on all models of the cars (example: 59 BelAir used the snap ins like you have found---Wagons/EC cars used the lil springy thingys.

Might have to talk to someone in the accy. dept.----I asked about them a couple of years ago and was told about $15 each (IIRC). Kinda pricey, but what can ya do---if ya need em, ya need em.