I would use 030 wire with either mix or straight CO2. Flux wire is for thicker stuff. In fact if your machine will support it, I like to use 023 wire. It makes for a whole lot less grinding. I run that in a Hobart 140 I have a 200 a 250 and a 440 stick machine. I prefer the 140 for any body work. Before you do anything, get some scraps of metal the same thickness of what you are going to weld. Then practice with your heat and wire speed. I've been welding for 50 years, and I still always set my machine with scrap when I weld any body work. Having a pile of scrap laying around that's welded around on is nothing to be ashamed of.
