FYI, there's a doubler plate on the floor above the cab brace where the shackle mounts bolt thru the floor. I'd be sure to install something there as well. Rather than nuts and bolts, the bolts thru the floor screw into a nut plate. That makes it possible to install mostly from below, once the bolts are initially threaded into the nut plate. This
photo shows the shackles as removed from my truck for cleanup and repainting. I thought I had a photo of the finished product, but you can see the nut plates sticking out from underneath.
There are no auxiliary bumpers between frame and cab at the rear.
