If the truck has sufficient power, does not smoke, does not drip oil on you driveway, just keep driving it. Old style Jaguars with the straight 6 were designed to burn a quart overy 1000 miles, and had a 7 quart oil sump. An engine overhaul will cost you a great deal, and since the oil you put in will not be expesnive (you are “changing” it every 4000 miles or so by topping it up), this is your best bet. If you live in an area where annual emission tests are required, keep your fingers crossed, but I doubt if it will fail because of the oil consumption. This is a good application of Wallmart house brand oil of the right grade, since you are constantly replenishing the additives by topping it up. Remember, OIL IS CHEAP!, every other option is expensive!