The flux core wire is not recommended for body work, although I cannot personally verify this.
Have you thought about gas welding? Oxy-acetelyne is a pretty versatile. It is not as easy to learn as mig welding, but I like the bead it leaves once you get it figured out. With the proper prep and flux you can even weld aluminum with a torch.
I have a mig welder (Miller 251) that I really like. Until I get my shop built, it really is a pain to use and I won't get it out unless I have a LOT of welding to. I use the torch for almost any welding I do around the house.
