Dave,
The number on the gear is S4S 5-P-262.
I contacted Potter Webster yesterday and he said it fits a Spicer 5650, 5750, and 5850 5-Speed Trans.
I looked in some of my Big Truck books for some application numbers and only found Trans numbers that had a different number on the end of those 4 digit numbers other than zero. (ei: 5652)
I'm guessing it will fit those, but not sure.
Wondering if you or anyone else out there would know what trucks those Spicers were in.
Thanks.