You can replace it with any DC ANALOG drive, but will have to do a lot of work, scaling dictation, feedbacks, etc. The 6010 works on the principle of Motor Field Control, rather than Armature control and is indeed closed loop. A one of a kind drive.

It Don't mean a thing if it aint got that swing.

Cool, Free, Johnny Smith courtesy of NPR..HERE
http://www.npr.org/ramfiles/asc/asc25.smith.asx