Rocker shims turned out to be unnecessary. The idea seems to be that if the rocker bottoms out the hydraulic lifter when the cam lobe is on the base circle, it will hold the valve open, so you get a shorter pushrod or shim underneath the rocker so that it leaves some wiggle room. On one of the valves it was clear that the clearance wasn’t enough but it turned out the lifter was buggered. I found a better one for that valve. Each of the rockers now moves up and down with no play but enough squish in each lifter that it seems like it should work. Each cylinder squishes air out of the spark plug hole nicely but I won’t really know until I try to fire it up tomorrow. Assembly is now complete.