Hi Byron
to the Surface Engineering Forum.
A photo of the gun would be good, see
here for help.
I think using 1/8 zinc wire would be best. 1/16 may be useful for the harder/higher melting point wires.
Many of the older guns are just as capable of producing good coatings, only problem is getting hold of spare parts.
Just remember the process is very noisy and produces dust and fumes that will make people sick if inhaled. Your substrate material will require thorough cleaning and grit blasting if you want your coatings to stick properly. If you are not familiar with the process, do some homework first