I have heard that the presence of a comm slot card in a 575 disables the PDS. Your mileage may vary. BUT THERE IS A SOLUTION!

IIe card in the PDS + a Farellon serial (appletalk) to ethernet bridge. I have one. (I beieve a couple other companies may have made these as well.

Honestly I never tried using the IIe card's appletalk capability with this bridge.