Flux core wire will make structually strong welds. In fact we prefer it over a stick for welding susppensions to axles. We have a wire feeder on a Trailblazer 440 and use .040 wire. We also have a 110 volt machine with flux wire in it to use outside in the wind on stuff not over 1/4" thick. But for body work, I use nothing but .023 wire with gas. Straight CO2 is ok, but I keep a bottle of mix handy when I weld in a patch panel that is going to have to be painted later.
