Dan,
I went back and looked at the return springs in the image from the GMC parts book I posted above. I copied the 1/2 ton number into my text by mistake. The 3/4 and 1 ton GMCs used the same 3697428 as your Chevy books have. Net is that all three different spring numbers are the same for 3/4 and 1 ton GMCs and Chevys.
Sorry for my short between the keyboard and my chair.
'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.
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