And the results are in: The timing set WAS changed, but the pan was never pulled. After pulling everything apart I discovered a scored damper and mangled bottom edge of the timing cover that were both contributing to my oil leak, a very loose timing chain, and a "custom" grooved cam gear!
Overall I'm glad I decided to inspect this stuff because it all needed attention.
Fortunately, I finally reached the end of the parts destruction and started reassembly. Ultimately, I had to replace the rear main seal, oil pump (Melling M55), pan gasket, timing set (Cloyes 3001K), and rework the timing cover, but the bottom end should be sealed up nicely now.
I also noticed that my truck has entered the stage of the project where it begins to be absorbed by it's surroundings and become a place for additional storage in the garage. At least it's still getting used as a truck I suppose...
And lastly, some fitment motivation. While the truck's up on stands, I somewhat mocked up where the rear will be once I finally add in the drop blocks. Even with only 4" backspace on the 9" wide rears, I still think they are tucked a little too deep. I'd really love to throw the wider rear end in there with the 6 lugs from '69, but for the meantime I am going to put in some longer studs (Moser 7/16-20 x 2 7/8") and 1/2" spacers. I ran spacers for years on my Malibu, and with the Moser studs I think I'll be alright. I don't beat on this truck anywhere near what I did to my Malibu.
Next up is getting the transmission reassembled and installed. I hope to have that done within the next month. Then maybe I can actually get back to painting the bed.