Most shock manufacturers have reference charts in their paper catalogs that list extended length, compressed length, mounting style. etc. So your assignment is to get close to the NAPA counterman and have him let you look through the catalogs so that you understand what the stock application specs are, then determine what the custom dimensions are that you have created and find something that would fit the mounting points in your truck and have the capacity to control the mass of the wheel/tire combo that you are using, Good luck, that is what I would do for my Ramcharger racer when it is time to select the shocks...I have a ways to go yet.