[HO455]

First off the new seat needed to be centered in the truck. (Photo #1) When I measured the width of the seat backs when mounted on hinge, the latch loops stuck out too far. About 65 1/2 inches and the door frames (real and imaginary) are only 65 1/16 inches (Photos #2 & 3) Fortunately the loops have about 7/16" of shims under each side and after they were removed the seat backs would then fit between the door frames. (Photo #4)

Now that I knew the seats would fit I measured the hinge and found it's center point. Then I measured the distance between the door frames and marked the center point on the edge of the new floor just before the drop off. I then lined the two center points up and screwed the hinge down with two small screws. I now needed to know the exact center between the two seat backs so I could line up the center base piece that the seat bottom bases sit on. By measuring the gap between the two pieces of the hinge for the backs (see photo #1)
I now was able to mark the floor knowing the center base would be centered on that mark. There was a bit of head scratching as the center base piece is in now way square or true. So a close approximation of its center line was decided on. And that was lined up with the mark on the floor. (Last photo red arrow)