I had two of those. The Evergreen model 300 "Rev to 486" clipped on to the A2386 and ran at 75 mhz. It needed a dos driver to load the clock tripler at boot up as I remember. I sold that long ago.
I still have the Cyrix 486slc clip on somewhere that runs at 50 mhz. They both worked pretty well, however are dog slow by todays standards.
I would still love to have a working bridgeboard setup for my A3000T again. It it ideal for it with lots of Zorro and ISA slots.