I think if your bed is off, you could very much do as you describe, assuming. But if you don’t, I think I was told putting the brackets and straps on the tank,loosely somewhat,then getting the tank close, with a jack then getting the brackets started with a few bolts,so that the bracket is lined up so your rest of bolts will all fit, then ensuring the straps are secure down. But this was for my 1980 and a long time ago. Not sure about 87. Because of my bed condition, pulling it off meant it would stay off and I would have to have fabricated something to hold sand. I think initially I didn’t think about the straps 100% so I just tightened them down, but they were not 100% lined up. That’s why I said possibly loose. I can’t remember if the strap tighten spot was accessible or not on when bed on. But yours is off