That's either a 400 series 2 1/2 ton, 450 series 3 ton, or 470 series 3 1/2 ton, with factory option Dayton wheels. I'd jump all over that one if I found it. The fenders on the 400, 450, & 470 series GMC trucks are larger than on the 300 series 1 1/2 ton, & 350 series 2 ton trucks. Also the 1954/'55 1st series "400" series trucks have two separate windshield wiper motors mounted above the windshield. And since the fenders are larger the '54/'55 "400" series trucks didn't use the square park lights, & fancy grille surround that the smaller trucks used. That truck should also have a 302ci. engine in it, if it's a 450, or 470 series.