I,ve looked at several lately and if your only doing sheet metal go with a 120 volt unit such as a Miller 135,you should be happy with it they also make the auto helmets. their better one also has the bigger window also practice,practice practice!
While this statement is true, the 120v should do fine for sheetmetal. I bought a 120 (not a top brand) and was unhappy with it (probably due to it not being a top brand) and when I had the need to weld something a bit bigger (thicker) I couldn't do it (actually you can but I was concerned about proper penetration on a critical component). If you know for a fact that you will only do body work welding and never anymore, then get the 120v, but a very good one.
But, if you even think you might get into some type of fabrication then go with a 220v. Of course if you can't get 220v into your garage then it is a moot point. I got a Millermatic 185 w/welding cart for $700 including shipping. I think you can get them cheaper w/o the welding cart.
Here is why I stepped up to a 185 (and a learning experience):
Those tire carriers run from $400 - $600, cost me about $60 in metal and another $20 in consumables. Not bad. The welder almost paid for itself duirng the first time of use!