hey this is what i weld every stinking day lol :
http://www.dayton-welding.com/skinner
Now, argon will make your wire run hotter, its good for flat welds and body work because its has better penetration in a shorter amount of time. Also if its "too" hot turn your welder down a hair and turn the wire feed up a hair. Now running straight c02 will make your puddle freeze quicker its also better for overhead welding. I run straight c02 as does everyone else at dayton welding. however on our cars we run 75Arg. /25 c02. Its easier on our little buzzbox too because we dont have to crank it up hard. if you can try straight c02 and make sure you get rid of that flux core if you are running gas. Thats designed for running with no gas. I recommend a solid mig wire of 0.23 for body work its perfect. Especially on the thin Z car. I just shaved my rear bumper and tack welded 18 gauge sheetmetal over the two side mounts and over the long oval shape off set in the center of the bumper and i welded in plates for the old bumper mounts. looks sick the little mig gun was perfect.