Just picked up a '47 CJ2A that the previous owner stated at idle was running on what seemed to be 3 cylinders and just recently started having coolant/water come out the exhaust. Once you got off idle, the engine seemed to smooth out. When I purchased, only ran it long enough to get on the trailer, off the trailer and into the shop. I suspect it is a head gasket, which is probably the best case scenario.
So far, to diagnose, I've done a compression test with the following results; 95, 90, 90, 90 with all spark plugs removed. Of note, cylinder 3's spark plug had fluid between the ground electrode and electrode tip, also the insulator seemed a little bit cleaner and more of a rust color. Before the compression test, I turned over the engine a couple of times to remove any fluid, which cylinder 3 shot fluid out. This fluid may have been penetrating fluid that was in the spark plug well from before removal though. Also, when compression testing cylinder 3, cylinder 2 shot some fluid out.
Oil has coolant in it, and after sitting in the shop overnight, the oil pan gasket appears to be leaking with coolant. Radiator has no visible level coolant.
My next move is to fill the radiator with distilled water, and pressurize to ~10 PSI, visually watch the combustion chamber for signs.