U Joint Help needed

[chev-obsession]

To make a long story short, I had my front driveline shortened which lead to rebuilding it. (Lesson learned pay the money and have the pros do it) now that we’ve got that out of the way, the shaft that came out of the truck is for a 69 Chevy c 10 with the 4 speed. I lost the caps some how so I cannot take anything in and compare it before I buy.... lessons being learned all over the place.

I got u joints from Napa and of course their the wrong size. Have a spare shaft that I believe came out of an automatic truck to compare mine, the u joints are significantly different. I’m not sure the the shaft in the truck that I had shortened is original to the truck which if that’s the case then I’m not sure what u joints it it is that I’m after.

Trying to find the right u joints, have you guys ran into this? Do you know what size, or a part number might be for the correct u joint? Here’s a few pics, looks like a p/n 3707775.

Any help is greatly appreciated