Crew Cab Chevy/GMC Question (Local Rookie)

[oldsoulyoungcat]

Hey guys I am just a 22 yr. old rookie and finally saved up enough change throughout college to buy myself an old square body truck. I have been searching to the end of the truck world to find a decent to good crew cab. As my internet search continues I found this custom truck on Craigslist for sale and the link is this; ( http://oklahomacity.craigslist.org/cto/4576332131.html ) The guy said it was a custom 91 suburban chassis/front clips with a 77’ short bed & crew cab on top making a three/fourth ton truck... but here is where I am confused. The VIN in the cab and it is titled as a k10? From my research and trolling and trolling of these forums I thought the only Crew Cabs built in 1977 were K20's & k30's?
Any help or information on the crew cab beut’s would help.