You may want to have a look at my post on installing Byers drives on my 1.5" Astrola mount for ideas. My understanding is that OptiCraft Machining drives are quite decent.
You have three choices as to motors:
(1) synchronous AC motors: reliable, easy to wire, but may require an AC drive corrector if you want to do astro-imaging. There is one company in the UK that still makes drive correctors but maybe it's best just to buy used on CN or AM--they come up periodically. Typically, for a 9" drive, the gear will have either 359 (pure sidereal rate) or 360 (nice interface w/Losmandy stepper controller, see (2), below). BTW, this is the solution I chose due to parts availability: those AC Hurst motors (see their website) have been available for decades,
(2) DC stepper motors: many prefer this solution. A stepper motor and controller board are required for each axis. Various options exist for controller boards. Some use the Losmandy controllers. Others buy this-or-that controller and optimize it for their system (requires a bit of electronics knowledge). This solution will also allow you to make your scope "goto", BTW,
(3) servo motors: this is the Cadillac solution and often used in much larger mounts. SciTech sells controllers and motors. However, I am concerned that, when eventually SciTech disappears (this is, after all, a hobby industry with few semi-permanent vendors), so too will availability of boards/ICs, etc.
BTW, the old Hurst motor wiring on my old (pre-Byers) Dec drive also became frayed and dangerous, and I had to replace the motor some years ago. These particular Hurst motors are rather expensive.
Regarding controlling the drives, given that I used AC synchronous motors, the wiring was similar to the Cave diagram someone posted above. I also wired in a hand controller for really smooth slow motion control.
Happy observing always,