I lifted the body off my Whippet with an engine hoist and a strap through the window openings. I lifted it up and set it down on 4x4's sitting on large jack stands. I then rolled out the chassis, lifted the body again, and lowered the jack stands down. Worked great without any help from anyone else.
Don't use the fender mounting bolts. They weren't designed to take that kind of weight. Even if they held long enough to lift it, they could give way with disastrous consequences.
29 Whippet Street Rod project
38 Chrysler Royal, original, unrestored