Replace bearings in BK12 & BF12 fittings

[Desertboy]

I have cheap ass bearings in my ballscrew mounts can I pop them out and replace them with better ones off the shelf?

I want to replace the bearings in the BF12 fittings first. One bearing squeaks when I'm cutting at 10m/min, so I thought replace all 4 bearings with proper SKF deep groove.

Then buy the correct angular bearings to replace the ones inside the BK12 from China and replace when they arrive.

1. Are SKF 6008 deep groove bearings what I want for the BF fitting?
2. Should I buy the rubber sealed or the Z version?
3. 6008 is the size right? So as long as I buy a 6008 it will fit?
4. Which size angular bearings do I need for the BK12 and how many?
5. What does clearance mean on SKF bearings, have a choice C3 or Normal.

Thanks