Thanks for checking and getting back to me Harold. For now I don't know whether I'll need it. Unless it is disassembled, it can't answer any questions. I'm glad to know it is an option.
Update:
No engine places are really calling me back, except Gallery Marine in Seattle, and they are only researching parts for me. Everyone is busy this spring and getting on a schedule means waiting a while. I am pressing on carefully. The head gasket quote was $181.00. A full set of gaskets necessary for head re-installation looks like under $500 through them. I talked to a nice guy at CSR in Des Moines and he felt that the hole in the gear case is to alert for leaks, particularly coolant leaks, but he couldn't be sure. I am not ready to shell out $200 an hour for mobile engine service.
[Real life interferes with troubleshooting progress]
I sent in an oil sample. No response yet. I had a problem with my ancient oil change pump, a Qwik Drain 112, so I worked on it a little. It's obsolete. Got it working, but it needs more TLC to survive. 55 cents for a gasket so far. When I drained the oil there was no water or coolant evident, but the engine sits at an angle, so small amounts might be stuck inside.
I have removed the valve cover and it and the valve train are pretty clean. Not much dirt or residue up there at all, which surprised me after doing valve adjustments on car engines. Clean air I guess. The breather is clear. I got some advice on removing the rocker arm shaft assembly. It can be done in one piece as long as I loosen the nuts evenly. Don't want to bend the shaft.
When I pull the pushrods will the tappets come with them?
Update 8/11/2016: This question is answered in a subsequent reply, but the answer is "no." The tappets can't be removed until the head is removed.
Yesterday I pressurized the cooling system with a hand pump and it held pressure surprisingly well. I plugged one heat exchanger hose and pressurized through the other. I didn't plumb in a gauge, but after 20+ minutes, there was still some pressure when I loosened the 'radiator' cap. After 10 minutes it seemed hardly down at all vs when I immediately relieved it. So, I paused overnight to make sure my test was valid. I think it is. The thermostat is still in, but they aren't typically air tight. My guess is that the issue would show up if I pressurized the oil system to a higher pressure. Can't really do that unless I run the engine.
Update 8/11/2016: With the benefit of hindsight, this leak test is best done with a cooling system tester that replaces the radiator cap and includes a gauge. Any leakage indicates a problem somewhere.
Later today, I should be collecting my penetrating oils and WD-40 to go back and start loosening the head nuts and bolts. I don't think I can learn anything with a compression check. I can also check the cylinders, block and the top of the pistons visually for problems. I will have the head tested for cracks and valve problems, to see if reconditioning is necessary. I already talked to the shop and they can definitely work on the Universals. I will have to remove the injectors and get them checked and reconditioned as necessary.