Thanks everyone.
I re-checked them this a.m., starting by loosening the adjuster on the 1 exhaust valve. I felt the rod spin and ended up putting it right back where it was. Man it's impossible to get two fingers on that one. I went nuts trying to position myself such that I could twist my wrist in such a way as to get a thumb and forefinger on it or any one of them, just to make sure...
Finally I said **** it. I backed off each screw and then adjusted them so the rocker feet were just touching the valve stem, and spun each pushrod in turn with the one finger I could reach it with. They all went back with the screw slots within a couple of degrees of where they started.
—Which is about what I expected, given that I got this engine from Carey Hines three years ago and it has not been run since (save to set the idle screws on the carbs).
Wish I'd thought to do this before installing it though. As Pip suggests, it's irritating as hell to have to turn it by hand when you can't see the front pulley or any marks thereon, and have to find "TDC" by the rotor position.
These cars are stupid.