A close-up of a front wheel would help. It looks like you have one of the "safer" wheel designs with a split outer ring, not the dangerous ones that come apart in the middle of the wheel. The bead ring will be facing toward the inside on the rear duals, so a close up shot of the rear wheel won't help identify the design. You've got the Dayton-style open-center wheels that will have a spacer ring between the rear duals. Different thickness spacers are available for different tread width tires to keep the sidewalls from touching each other.

The fenders and hood, and also the grill are wider on the 1 1/2 ton and bigger trucks to accomodate the larger diameter wheels and a wider track width on the heavier-capacity front axle.
Jerry


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