I have a drop in bedliner for sale that I took out of my '08 Silverado. It will fit the '07-'13 model years that have the extra short bed 5' 8". It's an over the rail model so it will not fit the GMC's, sorry. I've had it for about a year and it's in great shape. Asking $75.00, send me note if your interested.
Winterun