Around here 20,000 miles is nothing to put on one in a year. You have to remember this is mainly rule area. Also some of the best trucks I ever owned had way over 200,000 miles. So your theory is BULL. I drive the truck and it runs and Drives great.
I think a supercharger will pep her right up! LOL Not a fan of the flareside beds personally, but looks clean. If you need a stock unit and changer let me know. I have mine out of the truck.
I've got a Pioneer head unit with the mounting kit for that body style already on it too if you decide to go aftermarket. Good looking truck. I usually get bit by stuff with that many miles on it. It would be my luck that the CV joints would fall out of it the day after I bought it.