It has been eons since I retrofitted one of these, but I used a Mitsubishi system, the existing Electronic H.W. method is by a resolver on the H.W for the command, I cannot recall the motor details, but modern motor drives do not require a tach, these can be removed, if possible replace the tach with an encoder, using an encoder on the B.Screws if there is back lash is going to present problems. if you leave the tach in place, remove the tach brushes.
I once had all the documentation for the TapeTurn but it was scrapped along time ago!
Al.