I did it. A little trickier than I had hoped, but I think I got it. I had to jigger the position of the exhaust cam a bit to get the sprocket aligned with the dowel. It would be "almost right", then I would find that I needed to create more slack from the intake side (apparently slipping one tooth on the exhaust side (again!)) etc. For a while I was carefully keeping track of how many teeth I moved the chain. But ultimately I felt like I knew what I was doing and just kept moving things until I got the correct result. (I hope!) Marks on the sprockets are where they were at the beginning and cams in their same positions. All while the crankshaft was in TDC position.
It seems that the chain tends to slip its position relative to the teeth on the crank sprocket pretty easily (despite my attempts to prevent that), but it doesn't fall to the side, luckily.
I still need to loosen/remove the intake camshaft to change the oil seal, and button things up. And I will need to re-orient the distributor so the cap screws are still accessible when I re-set the timing, but I've done that before, so I'm not concerned about that.
I've read plenty about sealants for the valve cover. It seems like everybody has their favorite methods and probably many are similarly good, but I plan to adhere the cork gasket to the cover with silicone and then just put it on the head with a smear of grease.
It's all a matter of going through things once and becoming familiar with what's involved. Especially when you can't see all the mechanical parts.
Vince