When I did this:
http://www.bunchobikes.com/1952suburban15.jpg , I used 6' wide straps right where you see them. The only thing that got distorted was the front door, outer window trim. And I believe that was because I was coming up on the crane and didn't realize that I was getting stuck on the steering column and some wiring I didn't see. The rear window outer trim didn't distort and looks fine. I don't think you will have any issues, but, as with lifting any load, if you could spread that load, you'd be better off. In other words, the wider the lifting strap you use, the less chance you would have at localized deformation.
