Post a picture of the spindle and I can help - they are made here in my building. I've attached the 1997 catalog info for reference.
I have four of this "older" type, as shown in the catalog and I've been thinking of using them on a mini-mill also. I would discourage you from removing the motor, as these are dynamically balanced to incredible levels.
Also, make sure you have a 5 micron or smaller filter and a water/oil separator inline with the air supply, as particles and liquid will plug the .003-.005" orifices and cause the spindle to crash.
I can't attach all of the PDF files from the catalog, as they are too large. Send me a private message with your e-mail, and I can send them to you that way.