what the C/K stand for for a GMC Sierra C/K 1500
C - 2WD, and K - 4WD. Your vehicle is a 2WD/4WD. 1500 = 1/2 ton, (2500 = 3/4 ton and 3500 = 1 ton) although the load capacity might be considerably higher these days than when those monikers first went into use. (Your actual load capacity is in your owner's manual).
Thank you for your help.
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