Can Someone Please Explain Various Model Designations?

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Can someone tell me (or show me a link or something) of all the different models? I am in the market for a 72 chev/gmc and am getting confused with cheyenne, super cheyenne, sierra, cst, cst1500, when looking through the local ads.

i understand the c10, k20 stuff from the vin's but it's just the option packages i'm not finding any info about.

Also, is it my imagination, or do more GMC's come with the two tone paint scheme's (more than chevy's)? Just an observation...

thanks in advance...