Lazy K
Definitely does not have an O/D on the selector so must be the rare C6, i will double check the transmission code on the factory label.
Also worth noting that the truck has 204000 miles so i am sure the transmission is getting close to expiring, i tend to drive quite easily so might be able to nurse it along for a few more years if i can adjust the bands so that it does not hard shift into second each time, going into 3rd is fine