That's a great project. I'm thinking about doing that, but building the body.
A shock slows down the motion. It's a piston with little holes in it being drug through oil. It sucks up the bounce and jounce energy off of the road and turns it into heat. If you take them off, especially with a big box on the back, you could flop right over. I would double them. If they are in the way they are easy to move. Not being set up to weld is about the biggest mistake any handyman can make in life. If you are set up to weld, fab up some mounts that are not in the way. If you aren't, spend the $250 for a 200amp Lincoln or Hobart Stickmate and you can learn enough in a day to melt on adequate mounts.