The Beige G3s have a single SCSI bus that serves as both an internal and external bus. It only runs in slow-narrow mode (5MB/sec), so even though you can adapt a wide drive to the bus, your performance won't be that great.
The best way to adapt your wide drive(s) to a narrow internal bus is to purchase a 68 pin to 50 pin IDC adapter. Check Granite Digital.
www.scsipro.com
--Steve Rosenthal, Digidesign ETS