Since it’s pretty obvious what needs to be done to make the tank fit (try sliding it in. If it’s not fitting, trim something.), I’ll just show some pictures to confirm that it’s done.
Even though the rear spreader bar will cover the back side of the tank flange, I decided that my faithful readers would be disappointed if I left the flange alone. So, I trimmed it along the weld except on the passenger side where the weld doesn’t match the driver’s side. I’m happy with the gap between the body and the top of the tank.
I needed to trim the rails a bit as well as the flange. I have used 3/8 button head bolts, with weld nuts welded underneath the rail. We will be switching to stainless button heads for the final install. We won’t be using anything between the tank and the frame rails… we’re not expecting it to move enough to be a problem.
If everyone’s tank fit like this, the world would be a better place. We’re using a TANKS tank, part number 32-ZS. It has rounded corners like a stock tank and uses a stock-style twist-on cap.