Tom - That sounds like a 1 ton frame AD. 137" wheel base is 1 ton.
The frame over the rear axle should be straight with no hump in it. That is another attribute of the 1 ton. The 3/4 ton frame has a slight hump over the rear axle. The rear axle in both is mounted under the leaf springs. The data plate is incorrect. The data plate for 1 ton will read 7700 GVW for single rear wheel axle and 8800 GVW for dual rear wheel axle.
P.S. Did you ever finish the AD Suburban you were working on?
Whitman