Heavy-Chevy,
I took a look at the dope sheet for the Miller 180 and it says 5/16" for a single pass. This doesn't mean all you can weld is 5/`16" material, it just means you will have to weld it using multiple passes...very common.
If your wallet can handle it, you should try the Dual-Shield in .035 with mixed gas. You will really be amazed at how nice the welds on your frame components will look. They call this a all position wire, but I wouldn't run it any way but down hand.
If you can move your 4-link pieces around, and the frame or its components can be positioned down hand, your welds will be strong and look like they were factory made.
Stuart
