I doubt that 1 and 1.5 ton are the same, 16 and 17 inch vs. 20 inch tires, make sure to check out the ad carefully. The 1.5 ton ones are also cut in farther toward the center, look unusual on 1 ton trucks, 2 ton also used 20 in wheels, most I have seen are same size as 1.5 ton wheels.

'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.