Okay, now your posts are starting to make sense. In your OP, you were trying to determine if you had a run out problem severe enough to warrant a bearing change. Your method as you laid it out will not give you the information you seek. It is possible you have a bearing issue but it is also possible that the bearings are okay; you need to assess them.
This type of machine has two sets of bearings: the quill bearings that support the spindle directly and the drive sleeve bearings that support the drive sleeve that actually turns the spindle. The drive sleeve is driven by the pulley and transmits rotational power to turn the spindle. You need to assess both.
First, clean the inside of the spindle. Use alcohol and wipe it until your cloth or towel comes out clean, then dry it and don't touch it with your fingers. Clean your DTI (not a dial indicator) tip with alcohol and don't touch it thereafter. Mount the DTI in a sturdy indicator holder and position the tip of the DTI inside the spindle. Ideally, mount the tip on the back wall so you can see it. Preload the DTI by about 0.0015" and zero the dial. Now make a mark with a Sharpie on the front of the spindle and the quill itself. The mark on the spindle will rotate as you turn it and the mark on the quill will be a reference that does not move. When the two marks line up, that is your start and end point.
You will assess the spindle run out first. Be sure you've preloaded the DTI and the dial is at zero. Also be sure your Sharpie marks are aligned. Now slowly rotate the spindle by hand by turning the top front pulley by hand and make one complete revolution so your Sharpie marks align again. The DTI should return to zero. If it does, you can rely on the set up; if it does not then the set up is not reliable. In most cases, this is because the indicator stand is not solid. Either lock it down tighter or get a stand that is more rigid. If the DTI returns to zero, make a second rotation but slower and note any deviation from zero. There will usually be a high and a low point. Try to mark where these deviations are and note their magnitude. Your TIR will be the high value minus the low value. Return to your original alignment marks and make sure your DTI again reads zero. Make one more rotation and make sure the two deviations you saw before are in the same place and of the same magnitude. If they repeat then that is your spindle TIR and you can rely on it. Write it down.
Now you can assess the drive sleeve bearings by simply pushing back and forth on the pulley at the top of the spindle. As you do this, watch the DTI. It will deflect as you move the pulley so just note the magnitude and that is your drive sleeve run out.
For spindle bearings, acceptable TIR is in the neighborhood of 0.0002" or less. If it is more then a bearing change may be in order. Stock Chinese bearings will often run out more than 0.0002" when new so its a judgement call. If you do change them, replace them with higher quality bearings. You can go with ABEC 3 tapered roller bearings or higher. If you prefer, you can go with precision class angular contact bearings; the FAG bearings you listed are P5 bearings and are equivalent to ABEC 5 bearings so they are much more accurate than the spindle itself.
Drive sleeve bearings are not accuracy rated. They are simple radial bearings. If you replace them, get some deep groove bearings; they are built to take both radial and axial loads and will be more accurate in this application. Nachi makes good ones.
Bottom line: assess your run out properly to decide if there actually is a problem and how big a problem it really is. Then decide if a bearing change is necessary. If it is, pick good bearings so they last a long time and can sustain the loads your mill will see.
