It looks like the data tag shows #7300 for shipping weight.
https://olive-drab.com/idphoto/id_photos_m1031.php
That is for the M-880 which was the Dodge with Dana 44 front axle, Wisconsin engine powered Hobart 200 amp welder-generator, single phase compressor and 318 gas V8.
The M1031 SECM body was made by Able Body Company with a 9000 pound GVW. Shipping weight? 22 metric tons. Why? Because that is the displacement in cubic feet (87
based on water weight at 64 pounds per cubic foot.
The contract for the ABC SECM weight was based on the M1008, when the 1031 was finalized, it was given the HD load at 9200 pounds, hence the variation between the body and the chassis. The 1031 contract was expanded as the minus bed was a discount from GM so more chassis were bought than needed. Excess were converted to 1028s
Some early 1031 SECMs were made with salvaged M880 bodies with a small fuel tank added for the Wisconsin engine.
Hope this clears up the confusion.