Apologies for bumping an old thread. I arrived back home from my five day Indiana trip today and had time to look up more on the Wisconsin modifieds from my youth.

The group went by the "MRA" (Modified Racing Association)
A few youtube links below from 1986 and 88. VHS quality, but you'll get an idea of what they were like. Some cars had open cages, some had roofs. Different body styles. In a few of the clips, you can see a few cars emulating the flat-panel eastern modified body style. As a support series to the IRA sprints, they were more interesting to watch than today's brand of modifieds found in the midwest.

https://www.youtube.com/watch?v=HKz0x-XT7q0 (1986)
https://www.youtube.com/watch?v=tJ9DsidF99Y (1986)
https://www.youtube.com/watch?v=vm75L6mUM08 (1986)
https://www.youtube.com/watch?v=_ybDfNX0BtU (1988)
https://www.youtube.com/watch?v=WXtI6vwSEqU (1988)