could look for a ram charger rear door or a ford bronco for the hinges i would think either would support the weight you have with out a problem. And if you can see how they are set up shouldn't be to hard to dup it.

 

yeah some of the broncos have it where they come out sideways and they can hold some weight, Im about 190 and me a girl that was about 120 where sitting on my friends and it never had a problem, IIRC it was noticeable from the outside

 

there was a thread i seen awhile back, where a member made a tailgate/ tire carrier that hinged from the side.

btw the tailgate was made out of tubing to save weight and they reinforced the hinge mounting point cause the sheet metal is pretty thin on these trucks!

 

Try to find a Honda ridgeline in your local boneyard. They have 2 sets of hinges and 2 latches. One handle opens it down regularly and the other handle makes it swing to the side.