There is a weld or 2 and then a number of bolts. If you dont need to for sheetmetal repairs, I recommend you keep it assembled. It likely is as square as it is going to be.
You can block it up on the cross members. I would not be comfortable for it to rest on the lower edge of bed side as you have already concluded.
In my case I built a crib on casters. 4x4 posts housed the casters and then I ran 1x6 skirt and braced. I built it at a ht I could get under the side and low enough I could climb over the side. Rolled around my garage and drivewaay for a year or more like that. I would do it that way again.


~ HB
1966 Chevrolet K-10 | Ghost: formerly Flappy Fenders | In the Stovebolt Gallery
1962 Chevrolet C10
1962 Suburban