I raised my gas tank and it is still easy to get scrape or drag on! I will be going to a fuel cell in the near future. The main reason for the cell will be to shave the gas door. I raised my gas tank my self. The front crossmember has two rivets on each side. You have to cut these rivets and add a 1" spacer. I welded mine back in. 1" is the most you can go and the tank will be against the bottom of the cab. The rear crossmember has to be cut out, moved up and welded back in. Even with the rear crossmember raised it has to be notched for the driveshaft on both regular and extended cabs.If you leave the tank in the stock location, lifted 1" or not, I highly recomend a skid plate. Looking back, I wish i would have went ahead and went with a cell to begin with. It would have saved me alot of work, but then again I didn't have the money for it then either. I also didn't want to take up bed space, but have since decided to weld the tailgate up, so bed space doesn't matter now anyway.
I hope that helps.
Trey