Done.  14 days.  (bonus points: fixed a couple of gas leaks in the process)

Leak checked with air, using:
-bicycle pump;
-schrader valve (liberated from a broken bicycle inner tube) and screw
clamp;
-spare section of bleed line (GW 8x3.5 hose) connected to the vent line
manifold;
-nylon clamp plier to pinch-off the LH head vent, disconnected from the
vent line manifold.

Thanks, all, for your comments.

Now dreaming:
Alloy rims, oil temperature sensor, oil cooler, frame-mounted hitch, minor
body work.

gab