Help Identifying a Spicer 4x4?

[chevylookin]

Hello forum. I got this odd looking Spicer gear box from a friend who says another friend and his dad took it off an old Chevy truck long ago. The only identifying marks are the serial tag which reads: XC714 and then molded on the case which reads: CPI36-I or CP136-1. I have done a huge web search to find out what this is and how old it is and have returned nothing. Maybe farm equipment? The unit weigh about 50-60 lbs but its not that big and the driveshaft is rather long for a truck and is about an inch thick. I does look like it would attach to the old SM420 to the PTO cover. Is this an aftermarket old school 4 wheel drive for Jeeps and Chevy trucks?