I originally bought this kit so that I could do a quick fix on the cross-flow issue I've been having. The bed is just beginning to show rust on the wheel wells, and the cross sills underneath are very rusty. So the plan was that the kit would be a temporary fix, and in a year or two, I would take the bed off of the truck to repair it and while it was off, I could then access the fuel tanks and install new FDM units to fix the cross flow problem once and for all. Since I was going through the trouble of removing the bed and replacing FDMs, for an extra $100 or so per tank, I would replace them as well since I'm guessing 20 years is about the life expectancy of a fuel tank. I would be kicking myself if I did all of the above with out replacing the tank, and then a year after, the old tanks would start leaking.