powerscol is exactly right - the issue is that I can't get the shaft off of spreader. There has already been lots of penetrating oil, force, cussing, heat, etc attempted.
The idea was to buy tractor side half shaft that would fit the one rusted on. My local TSC does not offer a shaft with the same cross section as this one (thus the reason I asked for help identifying the shaft).
I have 2 other alternatives:
1) Take the u joint apart and connect another shaft that way (will require some research to see if the yoke will fit the shaft).
2) Cut the yoke off and replace - research to see if a replacement PTO shaft will fit the shaft on the spreader.