I had an 8' Fiberglass shell I would put on/off a regular bases by myself. Just unbolt the 6 small screws, lay two 2x4x9' in the bed, crawl up in there then use lift one end up at a time to put the 2x4 under, crawl out, put each end of the 2x4 into a 5' sawhorse and done.
After a couple years of this, came across an old manual boat winch so bought two double pulleys and 4 single pulleys, put eye bolts in the roof and then just used the winch to lift it up. Was so much easier plus didn't have anything on the floor in my way. Everything was positioned so I could still park the truck under it.