While the paint was curing on the tub, I plucked out the engine to tackle the oil leak. After splitting it from the transmission I put it on my engine stand and flipped it over to tear down and see what was going on. Turns out the leak was coming from one of the rubber tubes that are in the bearing cap/block seam and wasn't the main seal after all. Probably a lack of sealant or they were cut too short? I also confirmed the cam bearing cap was intact and the brass plug was holding. Regardless, I replaced the seal and plugs and buttoned up the oil pan. I re-installed the powerplant complete with rad (works great!) and have ran it over 2 hours with nary a drop of oil from the rear.
Now I can confidently put the tub on the frame
Again, 2 pictures wouldn't load?