chev235,
Technically, there should be only .023 or .030. wire. The smallest diameter flux cored wire would be .030. The flux core wire doesn't require a shielding gas, but does require a higher amperage setting to burn the flux and make a proper weld.
To successfully weld the thin sheetmetal, you need minimum heat input, which means minimum amperage, which equates to small wire diameter.
.023 solid wire with the shielding gas you noted is the most friendly for these thin body panels. It doesn't get 'skinnier' than this.
Stuart
