im assembling my 68 chevelle dash and i came across some electric connectors i dont know what they go to. they are black plastic wire ends that go to different round sockets in the back of the cluster. they have a single wire and no metal parts they look like they might take a bulb but there is no way to twist and lock a bulb in. there is just two small holes on eather side. all i can think of is they take a special bulb.any ideas.