Rural King lifted mine with a forklift and we tilted it back into the bed. Getting it in without the forklift would have been near impossible.
Unloading it involved gravity and terror. That's a LOT of weight teetering on the tailgate.
I helped a guy from work load/move/place a gun safe about the same size as gpa's. (Maybe 600lbs was an exaggeration ). Gander rolled it to the tailgate on a dolly, and tilted it in. We got to his house, unloaded it, took it around the house through the grass and down the hill to a walk out basement using a regular air tired dolly. I think the tailgate can handle it. That's roughly the weight of 3 guys sitting on it.