YES i HAVE BEEN NEEDING ONE OF THESE for years but just could not come up with how to make for the weigth being pulled up the ramp tailgate. I would appreciate pictures or recomendations on how you built your game hauler.
Not sure which part you need help with, but if its getting anchoring points, some folks, such as use the tie down points fixed in the bed floor.
Put a a length of chain between the two tie down points and then fix your winch to the center of it.
If you are looking for something more permanent, you will need build some sort of frame and anchor that to the truck and then bolt the winch to it as below:
(Pic is from another site and shows a set up which belongs to a British stalker who posts as PointBlank)