I have dealer installed tubular side steps on my 05 cc 4x4 8ft bed Silverado. Does any one know if Chevy sells a set of steps that mount behind the ones I have so I have bed access. If not who makes the steps for GM?

I've never seen anything advertised as a extension to the factory one's. but you may be able to find a aftermarket company that might make a 2 piece set and just buy their rear set. Most of the full length steps or nerf bar's are one piece, mainly for mounting purposes I think. I have a set of Putco's on mine that are full length and they work great for me. You may have to take the factory's off and sell them and buy a full length set.
Good luck
DD

your wanting the wheel to wheel steps, Westin makes them

If you have a dually, WAAG makes a wheel to wheel with kick-out. I'm getting ready to order a set for my truck.

N-Fab.com makes a great tubular step and they have a model that goes back to the rear wheel well.