Just to stir the mix, below is from June 1954 edition of the GMC Master Parts Book covering 1939 through 1954. The bad news is that is doesn't indicate what is "older model" and what is "later model".
'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.
