I was given a 1953 Willys M38A1 Army jeep that had been left sitting on a farm, was vandalized and pushed into a dry creek bed which later flooded. The engine was seized. When I got the Jeep home, I pulled all the plugs and squirted each cylinder liberally with Jet A jet fuel and let it set for a few days, adding more each day. After a week I put a breaker bar on crankshaft pulley and rocked it back and forth and got slight movement. That worked up to rocking entire jeep, in gear, and got the engine to turn over. Throughout the process changed to MMO for more lubrication. Ultimately, got it loose enough that I could turn it over with starter after fogging cylinder walls with oil.
Next step was starting with starting fluid and getting good oil pressure. With all the Jet A, penetrating oil, regular oil in combustion chamber, it smoke like no tomorrow for a a good bit. Once it was running and good gas supply provided, I started and ran it having done nothing to carb. A buddy suggested using ATF fluid drizzled in the carb. It filled a large hangar where we were working with smoke to the point you couldn’t see ten feet!
After this treatment, the engine settled down ran smoothly and quietly. Other than changing oil, I never did anything else but change the water pump. I cleaned the old jeep up, fixed some rust and body damage and painted and went through all brake system with new and changed transmission, transfer and differentials and flushed them. I finally painted it semi-gloss OD paint as it was from factory.
I drove that jeep for several years before trading it for another earlier model. It was still running and going well the last time I saw it. The only maintenance was changing the clutch pressure plate and servicing.
And I ran MMO in both oil and gas in all my old Army jeeps.