dcains,
I don't think Orion is going to be able to help you here. The Clasic and XTI have two different DOB bases. The XTI has magnetic encoders built in to the Azimuth and Altitude bearings from the factory. The Clasic has no provision for these, and Orion does not offer a kit. Thats why they carry the two different lines.
You may have to look at adding an after market from another manufacturer. A company called JMI has such of a kit. It will be as expensive or more as your scope was though. Contact them and they can quote you a price for a complete system with computer, encoders, cables, and mounting brackets.
http://www.jimsmobile.com/buy_ngc.htm#Complete%20Installation
JJ