Well, she runs!
This weekend i had the chance to work in my buddy's shop and we got the old engine pulled, and the new one put in. We figured out what was wrong with the first one as well (besides a cracked coolant passage in the head) - the oil pump shattered where it meets with the distributor drive gear. Either I neglected to tighten down those two bolts enough, or they had worked themselves loose enough that the hex end and socket got out of alignment. The pump still spins fine, it's just that connection went bye bye. So that was my bad, either way. I'll never make that mistake again!
But overall, it feels good to have a better, more thoroughly rebuilt motor in the truck now. After I finished building it, all accessories, etc, we measured 70lbs of oil pressure cold, which is great.
We figured out that this blue one is actually a 1970 block, even though it apparently came out of a 1979 van. Swapping wasn't too bad, just 18 hrs for the full maneuver. The torque converter and shaft seal on the transmission both looked like they had been replaced at some point - both super clean.
Got it running, though am chasing some serious vacuum leaks. The intake is a spread bore, and the carb is a square bore (rookie mistake), so perhaps that's the issue. I have a simple plate adapter in there, but maybe that seal isn't good enough. But it runs! Coolant temps are good, after replacing the thermostat and adding a little hole to it, and the transmission leaks like a sieve, but dang it feels good to drive the truck home, and have it back in the driveway.
The new engine is very responsive, sounds great, no ticks or anything. The left bank exhaust is still smoking, but I think that's just accumulated coolant from the last engine getting burned off. It seems to be calming down after a short drive or two.
I already found a use for it - hauling the old engine. I assume the crank would need to be machined to be usable again, along with the rod bearings, but maybe I'll save portions of it? Not sure I have room or capacity to store all of that, but maybe. The block should be salvageable, but also very scrappable. And one head has a crack in the coolant passages. Any suggestions on what to do with it?
Still need to get some small stuff done with it, but it's a huge milestone - I've had this thing for 2 years, and it finally feels like it might actually be usable now. Fingers crossed. I'll post some more photos of the final swapped engine soon. Time to put my feet up.