I am trying to hunt down a GM Ring Gear and Pinion with the numbers 3873532 ring gear and 143257 pinion. I don't know what model of GM this went in but all my web searches point to maybe some kind of '79 model. This isn't for a vehicle of any sort. Its for a water well drilling rig rotary table. They used GM parts back then when they built this equipment. Any help would be greatly appreciated.