Quoted from StoneyCreek:the 'slide from the back of pickup to the ground' part sounds easy, but it's a 2.5' drop! Are you recommending pulling out the machine and slowly lowering one end down to the ground, and then swiveling it and lowering the other side? We're talking 270 pound (well, less without the pallet).
Have the pallet (bottom) closest to the tailgate. Slide backwards (slowly) until it "tips" up onto the pallet, standing upright on the ground.
You should be able to hand truck it around after that.