I walked the full roof off my 72 K5 alone when I was about 34 years old..it was a struggle and I vowed not to attempt it alone again..
Those full roofs are heavier than the 76 up ones that are shorter--mine was a double walled one too..must weigh roughly 150+ lbs ?..
I bolted a 2x4 across the middle of it after unbolting it, and used my back to lift it up and grabbed the 2x4 with my hands and I had backed the truck up to a retaining wall that was as high as the bed floor and put two sawhorses behind the truck to lay the top on,I just walked out backwards and laid it on the saw horses.. ..felt like a turtle!..
I had a friend help me put it back on too..my back only was good for that one time..
When I took the top off a '75 2wd Blazer I had,I made up a device to slide in my engine crane that I bolted a 2x10 too,then I could just roll the crane in from behind the truck and center the board on the top and jack it up a bit and drag the crane back..I used a ratchet strap to ensure it wouldn't slide off sideways or off the crane boom..