Hey Wrenchbender, I called Delco and referenced the CS 121 and they were not able to tell me a car or truck that they were originally put on.  I'm looking for a make and model number so that I can go down to my local junk yard and get one off an old car for about $25 rather then buy a new one for $100.  Do you have a CS 121?  If so, they said if they had a PART NUMBER off it they could cross reference that with a vehicle.  Thanks.