I have a 1968 Cutlass that has a bad tail light bulb socket, this is the one that is used for the directional and it has 4 wires going to it, 2 brown, 2 yellow.
All the local parts stores only carry a 2 wire replacement...that will not work.
Do I need to special order one or is there a way to use the 2 wire.

 

I am thinking the two brown are connected together and the two yellow are connected together, so that another socket wires off of this one. You would just have to have a splice to join the two sockets and the lead in wires.
The ground joins from metal to metal contact in the housing and socket.

 

If the socket is just corroded there is a small round wire brush you can use to clean the inside. Then just use some wd40 to free up the contacts so they move in and out and make sure the little springs behind those contacts are good. Wipe dry and then add some dielectric grease and your good to go.

 

Two of the wires are power in and the other two are imply jumpers to the next socket. You'd be able to figure this out if you had a Chassis Service Manual with the wiring diagram. All you need to do is connect both brown wires to the brown wire on the new socket and both yellow wires to the yellow wire on the new socket.