Back on this again... an update. After trailering the van home, and finally getting the timing close enough to get the engine to run again, I bought a puller and finally removed the crankshaft pulley, so I can take it to my parts guy to ensure he can order me the proper replacement.
The purpose is to replace it with a pulley where the timing mark has not slipped out of position, thus I can nail down the timing precisely. Up until now, I couldn't visualize what the pulley failure would look lilke, and believe it would be helpful to others now dabbling in the early world, identifying 45 year old parts suffering stealthful deterioration. Hopefully soon, I'll have a good 170!
Here's the pics... FYI, there is a thin band of rubber or nylon (?) that's supposed to be tightly sandwiched between the hub and the pulley ring, just inside the red ring I added. Notice the chunks missing from it, the relocated timing mark, and the grinding on the back of the pulley where the puller bolts go... there was also a considerable groove from the timing cover seal, so I guess I can finish with the rest of the gasket kit I bought in the summer!
When that rubber ring dries out, the pulley ring can just slip around the hub (I can't do it with my hands, but...). Eventually, the pulley ring slips right off the hub, and chunks of metal become part of the catastrophic failure.
I left the crank pulley with my parts guy, and I'll get a new one from him locally on payday... costing me $175, but I guess I'd have to deal with shipping costs otherwise. Should be able to dial in the timing properly with no guesswork!