Looks like its probably going to bjf pending a few questions. You guys pretty much thought this through already but here goes. The box on the back is mounted on a shock/piston, so it slides with the door to account for the difference in pivot points. It mounts to the door, so the door opens and stays open (shock) with the bumper mount. My truck is a 94 Port of Entry with a half back door and flip up tailgate, and this carrier was not designed to work with the half doors as the upper door hinge placement is different. The previous owner fabricated two spacers to make it work with the door. They sat between the hinges and the body/bumper. I didn't realize that the blocks on the shock weren't Mantec factory, will look to see how they're mounted. I would guess (as did others) that he used them to account for the recess in the POE door design. I have the flat plate somewhere as well, will take a look for it. I recently went with a RockWare rear bumper/tire carrier which I love, though the door swings free now. I'll get more pictures today of the plate and piston mount and make sure it can be removed to original configuration if it's not as designed.