trailer-made-scratch becomes boneified tool

[Frank S]

Thank you for your thoughts. The hydraulic crane you show with it's slanted post will require some thinking about as to the vectors of the forces involved. I was envisioning a little platform with a leg that would fold down when the crane is installed that will take the weight after the trucks springs take a bit of load. I have not yet determined where the crane will have to mount to clear the tail gate and possibly not obstruct the tail light. I am not sure as to the legality of a permanent mounting plate that is 8'' wider than the truck body? The mirrors fold, this would not.
Rob

The reason for the slanted post on the crane in the picture I would guess is because what they had done was because the crane was most likely nothing more than the post boom and cylinder off of a standard engine hoist. Giving it a recognizable geometry. having 2 angled drop legs negates the twisting forces which would otherwise be transferred to the horizontal stem of the mount meaning they did not require a much heavier mounting.
the legality of having a permanent mounting extending 8" beyond the body should not cause an issue as long as you did not exceed maximum width. In the old US DOT laws before it was even called the DOT stated loads could extend 9" beyond the vehicle on the right side and 6" to the left. These dated back to the 1940s.
If you look around and see pickups with glass delivery frames mounted on them you will see most extend about a foot to both the left and the right. with the framework extending down to just below the centerline of the wheels. Also plumbers trucks often have racks on the right side to carry long pipes down below the bottom of the passenger door.