Been welding for about 10yrs, currently using Miller 175, though haven't tackled anything of this magnitude. Most of the steel tube is 3/16 wall and I'm fairly comfortable with the MM175 at this thickness. Plan to use .035 wire and 75/25 mix.

There are some 1/2in gussets, however, so I'm thinking those will definitely need multiple passes. Also will probably do multiple passes on all the high stress joints regardless of thickness. Can someone pls describe the procedure for multiple pass welding, for example, welding 1/2 plate to 3/16 wall tube.