I think you got a great deal on your compressor. As far as your isolation pads, I would go to an industrial rubber supply shop which specializes in conveyer belts and rubber mats and get a few inch thick pre-cut stripes of rubber. One inch will probably do. I don't know how heavy your compressor is. Then fasten them down to your plywood. The best pads ever made :-). I hope this will work out for you.
'67 Camaro RS