mark, from what i am aware of there were[at one time a BUNCH of years ago !] only a couple of vendors for what you are looking for. i'm assuming[as you can guess by the use of that word....] you are refering to a double contact socket using an 1156 style pin index[pins 180* from each other and on the same plane] with an 1157 base size. if i recall, these specialty bulbs were intended to be used in early ford tail lites, possibly somewhere around the 40-50 model year as well as other makes. i think the 6v double contact sockets you are refering to were used by lots of manufacturers , but the light was not grounded thru the base - it used 1 hot & 1 ground pigtail in the socket to complete the curcuit, thus the 180* pin layout. it didn't matter which way the bulb was installed. as to the vendors of these bulbs, it's possible that one of the early electrical guys had these made specially for this application. ron francis perhaps ? i didn't check that website to see what is available, so i'm just guessing. i would rather bet you will probably have to re-socket your tail lites. sorry i can't be of more help. merry christmas to ya ! eric