Hello,
We find all the characteristics of many skywatcher mounts, ratio, angle of stepper motors, even the number of teeth for gears on the internet!
On Youtube there is also a lot of information!
For stepper motors in principle the angles used are 7.5 ° and 1.8 °!
You can keep your original motors, the main thing is to remove all the gears, and to mount pulleys (GT2) with belts to remove the maximum play in the reduction.
Pierre