I modified the mounts that came with my 86 B so that I could use the factory tow mirrors in conjunction with the pillar mirrors. When I'm not towing i can fold them inside. I just welded a strip of aluminum on top of the stock frame to extend the tow mirrors out further. Kinda the opposite of standard desires but very functional when towing.
Dragginmazda86 (Dave), please tell us what you did to get those MX6 mirrors to work. I went to the salvage yards today and test fit one, and it didn't seem to line up at all. They look awesome though.