Hi,
All pulleys and belts are from beltingonline.com
Nothing special, ball screws machined normally. 2 grub screws on pulley. A drop of instant glue on the shaft. If I was doing it for myself i would file or drill the shaft where the grub screws are. Now it's more forgiving for mistakes

On the big machine I am building now for myself I use only aluminum pulleys as it would be geared 20:30 t and the rotating nut is heavy so I don't want to have too high inertia. These I bought from China as here prices are prohibitive. Aliexpress.

Normally you don't need any special machining given that the motor plate is not thicker than 10mm.
On the Z however is good idea not to make it too strong especially if geared for some reason. Cause hitting the bed can do some damage especially with strong motor.