My "69" C 20

[muley]

I don't even know if i'm doing this right, but here goes...

I got lucky and fell into a pickup I wasn't looking for. And I love it!
A 1969 C 20 3/4 ton Longhorn. All original. 350 and sm 465 trans. I don't know yet on the rear end. It's an Eaton with the pinion bolt, but I've read that both 52's and 72's had the bolt, so ??? It's been well serviced since it was new as I'm the third owner, with paper to prove it. It even had the original warranty folder in the jockey box filled out by the original purchaser 30 miles from where I live, and the dealership is still in business.
If anyone knows a visual difference between 52 and 72 diffs, I would appreciate it.
Thanks