I don't know that Chevy had all the options that GMC did for '57 3/4 ton wheels, but below are the specs for all 3/4 ton GMCs from 55.2 through 59.

The first column is "Year Series". '57 is the letter T.
The second column is "Model". 15 is the regular 3/4 ton truck.
The third column is "Rear". EDIT My guess is that S is for Spicer (later Dana) 60. S = single rear tire, D = dual
The rest of the columns are self-explanatory.

There are a bunch of wheel options.
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Last edited by Bill Hanlon; 08/20/2023 2:24 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.