Thanks for the responses!
I am referring to the pillars between the rear doors and the cargo area. I think those are C. Well, the Tahoe used to be a border patrol vehicle, and it pretty much looks nothing like that anymore lol. However, I don't know why I missed the damage to those pillars when I first got the truck. Pretty unsightly and now I see it all the time. I think I will take a picture and post it when I get home. I've seen other Tahoes with similar history(Police or border patrol), and the C pillars look normal. Perhaps a cage used to be there? K-9 or something? Either way, those pillars look like toast...they have to go.