Dave, I would say the best way to go is the route that has been done by a few already. That is cut the floor from a 4x4 and mate it up to a Mk1 or Mk2 shell.

On the hard stakes I would put it some place close to tying two eggs together!!

If its just one summer you have free then forget it mate, it will take ages and pots of money unless you are very gifted with the mig set and angle grinder!!