The 8 lug wheels are the giveaway, it's a 3800 1 ton Apache. The Vikings either used a large 5 lug front/10 lug rear, or a larger 6 lug all around. They also have much wider front fenders than the 1/2 through 1 ton trucks. There should be a serial number plate spot welded to the drivers side door pillar, usually on a windshield frame part of the door opening. The number should also be stamped on the drivers side frame rail, near the steering box.
