Here is how I did it by myself on the 79. Original gate was missing and the hinges were in still installed in the body. The spare gate was in the back cargo area uninstalled.
*****Big plus for me is that gate was empty.... no window, or lifter assembly.*****
1. Remove hinges completely. Whether they are on the gate or body
2. Installed the tension rods into the bottom of the gate slot.
3. Next I put the rods into their little pocket on the lower hinge.
4. Then loosely bolted the hinges to the gate.
5. Next Because the gate was not full of everything I lifted the gate onto the rear of the jeep and loosely latched it.
6. This allowed me to lean over the gate, line up the bolt holes with a slim screw driver the bottom hinge bolt hole and using the longer bolts.. start them into the body.
7. Get them snug enough to operate the gate for adjustment
8. Then I put all of the stuff that weighs the gate down into the gate.