Sawdust46,
Good to see another Deco era bolter in NC, welcome.
I searched the Chevy aftermarket suppliers for mirror arms as well and came up with nothing. It appears that the vendors only focus on 1/2-3/4 ton trucks. The arms are not the same.
My sugestion is to look into military vendors or other makes such as:
http://www.vintagepowerwagons.com/pdf/parts/18body.pdfOkay folks, please don't attack me for suggesting to put Dodge parts on a Chevy.
I think that most remanufactored mirror arms are based on the King-bee originals and they were fairly standard issue for most truck makes. Do your mirrors mount on the upper door hinge?
I hope this helps in your search.
Paul