As already mentioned cut a sheet of 18mm plywood to lay on the floor. It spreads any point loads so as you dont put dents in the aluminium floor and you can slide the engine in and out without worrying about any damage. Drain as much oil as you can before loading then strap the engine down good and tight. Take some off cuts of 4x2 to use as packers and try to keep it upright. Weight loading is no problem. I had a pallet of bricks in the back of my 90. Loaded them in one at a time. Dont know what they weighed but the springs were a tad compressed.