We put some 2" foam on the ground as a pad and rolled the tub onto the fire wall to clean up and finish under neath (easier than working upside down!)
We made a wood frame to support our "new" tub while a bunch of stuff (dash, brake booster, heater assembly, etc) was installed. This allowed the frame to be stripped, POR-15'ed, brake lines, fuel lines, all suspension work, etc. to be done at the same time. So much easier to work on the frame with the body out of the way and it was nice to remove stuff from the old body and install right in the new one. We lifted the front of the tub and supported on saw horses and used an engine lift to hold up the rear and rolled the finished frame under.