Be careful with pressure testing, especially if the truck is running an original-equipment radiator. Most everything produced before the late 1950's had a maximum system design pressure of about 7 PSI. Getting energetic with a pressure tester while looking for a cracked head or a leaky head gasket can hand grenade a radiator or heater core. I like to pump up 5-6 PSI and leave the pressure on overnight, then spin the engine with the spark plugs out the next morning. If coolant is going into a combustion chamber, the plug holes of the affected cylinders will squirt.
Jerry
