I had redone my 75 with a tube gate, but was able to re-use the hindges
just take a 3x3" x 1/4 inch peice or angle and weld it to the cab/latch/fender support corner near the gate, the plate the ploor with some 1/4 inch and spread the load into the nearest body mount, mine lasted and was pretty beefy,
I dont see why it could not be done to the factory tailgate, however the factory hinges are all wrong for how you want it to close or funtion