I have a 1977 f-150. When driven every day the truck runs perfect uses about a qt. of oil every 2 months. If the truck is not started for about a week white smoke just boils out of the exhaust like a mesqito fogger for about 2 or 3 minutes.
White smoke means water is getting in the combustion chamber somehow. Black smoke is fuel, blue smoke is oil. Can't say where it's coming from, but white smoke is definitely water. I would drain the fuel bowls and gas tank myself before looking internally. I'm no ASE tech, just my .02
You probably have worn valve guide seals. But if you want to rule out coolant problems, there are two ways. One is a bit quicker than the other. 1st way is to remove all spark plugs. Pressurize cooling system with a pressure tester. Let it sit over night. Crank the engine over and look for coolant spitting out of spark plug hole. 2nd way which I like better is to get a compressed air into each cylinder and watch for bubbles coming up through the radiator neck. Valves need to be closed, so either pull the valve covers or turn the engine over till your coming up compression stroke. There are block testers that turn the blue dye to yellow, but Ive found they arent always accurate. Any spark plug you remove that has rust on the threads and electrode, that cylinder could be compromised with coolant
Ditto on the above... also just check your dipstick for gray or milky oil. some condensation is typical if your just doing short trips, but if your oil is graying, your probably looking at a head gasket or cracked block (if its white smoke). The plastic/rubber (whatever they are) valve seals get brittle over time and are notorious for breaking. That allows oil to get down into the piston while the truck sits (especially if its sitting on a sloped driveway).
IMHO, a quart every two months; now that much I could live with. Especially if you're driving it every day.