Thanks for the post 4speed. I hope I am not steeling the OP's thread. Another option is to take 4 pieces of all thread and attach them to the body with angle brackets attached at the cowl and with makeshift points at rear. Then attach the other end of the all thread to chains attached to the ceiling joists. When I did the floorpan/firewall swap on my '49 Merc I picked the body off the frame this way. It also allowed me to safely work under it and slowly lower it back down on the Buick floorpan as I trimmed it to fit. All done without any outside help. I had an 8 foot ceiling in the basement which made it simpler to rig up.
You can just barely see the allthread but I think you will get the idea.