I really considered a tailgate pad, the Dakine DLX specifically based on my research. But too many reviews of all of the pads discussed scratching the truck paint under the pad, and the bike downtube. Soft padding, wedges to stabilize the bike, etc. only help so much, and the paint wear is really bad if you leave the pad on constantly.
My Silverado is the short bed as well, the bike would fit laying down diagonally but I was not happy with that approach as it was unsecured. Standing the bike up, rear tire wedged into the cab corner, front tire turned into the tailgate corner, and a tie down holding the bike worked for a while but I still wasn't very happy with it. I finally broke down and ordered a hitch rack.
Last week, the bike shifted somehow, even though I had it tied down the same way as dozens of times before, and fell over the side leaving a few inch scratch down the side of the truck (brake lever)
My hitch rack arrived 4 days after the scratch (first scratch on the new truck, guess it was time).