Need help soon on this

[Drive-In 4x4]

Hello big fan of this place but haven't been around for awhile. Work to much play to little but that may change soon. Anyway I am going down to Oklahoma to look at a 72 Cheyenne long bed VERY soon. My question is this and maybe it's nothing but it's about C10 verses C20's...I'm thinking of buying this truck and it's a C20 and the lady says that she almost sold it recently but the guy didn't want it because it was a C20. Why was that a concern? Aren't the C20's a heavier duty truck? Where on the truck other than the emblems does the truck indicate C10 or C20? Is it in the vin number or just the sticker in the glove box? Also what is the difference between SUPER Cheyenne and Cheyenne? This truck has a Big Block that's original to truck and that's why I want it because I need a truck with some POWER BABY...YEAH. Anyway why would someone prefer the C10 over the C20? Need answers to these questions soon...Thanks