Around the valve stems and push rods the penetrating oil of your choice. Kroil, marvel mystery oil, pb blaster. You want something that will lubricate and penetrate any sticky deposits. Even on modern motors people have been having problems with varnish from old gas, causing stuck valves ,bent push rods carb problems. You might do a search in the engine forum for advice on reviving engines with least amount of damage and ways of determining the polarity of you r truck as they were positive ground from the factory.
