what a friend ran into
What a friend of mine ran into as he was taking the body off his 47 Plymouth Sedan, was years of build up, tar and grime. He was telling me that stuff stuck like glue. I he went back several times making sure he had all the bolts out.. The sling I read about works best, no damage to the body.
You might want to look into building a gantry, if you plan to do another car.