I just saw a guy run a smoke-machine thru an engine's oiling system to get a visual on any oil leaks, before any other work commences. So connect the 2F PVC system from the pcv valve to the valve cover. The smoke can also be applied in the cooling system. It was a real shop, with a dedicated smoke machine.
A cooling pressure leak-down test would be possible with a flat plate covering the water pump and thermostat holes, adapting a custom fitting for a radiator cap to use the already available pressure test.
So, the cooling pressure test, the visual smoke-test for the oil, and a compression test for the combustion chamber - a simple engine report card that could be helpful to not get off-track. That covers every possible leak-location on the head gasket, and around the oil pan / front cover, front and rear main, and side cover, and all the core plugs in the castings. It would be harder to test the valve guides, which might leak exhaust into, or loose vacuum to the valve cover, but I could imagine someone making that happen as well.
A cooling pressure leak-down test would be possible with a flat plate covering the water pump and thermostat holes, adapting a custom fitting for a radiator cap to use the already available pressure test.
So, the cooling pressure test, the visual smoke-test for the oil, and a compression test for the combustion chamber - a simple engine report card that could be helpful to not get off-track. That covers every possible leak-location on the head gasket, and around the oil pan / front cover, front and rear main, and side cover, and all the core plugs in the castings. It would be harder to test the valve guides, which might leak exhaust into, or loose vacuum to the valve cover, but I could imagine someone making that happen as well.