Sorry - I thought I had responded.

In the years since I started working at Spring City Cycle in your hometown in 1990 until stopped working in shops in 2014, I've seen and adjusted dozens of Suntour 7 speed non-Microdrive bikes with non-Suntour sprockets that shifted as well or better than with Suntour FWs.

I have never seen anyone attempt to get a Microdrive 7 or 8 speed system to work with anything else - these systems were not common. Even less common was Superbe Pro with a freehub. Some shifters designed for the MTB 8 speed system would also work with the 7 speed cassette version, if you look at the 1994 Suntour catalogs. That 7 speed spacing was different than the 7 speed Accushift freewheels, but I never came across anyone swapping it for Shimano hubs to experiment.