Tool post grinder - video

[metric_taper]

In my ignorance of the many projects I've seen making tool post grinders, how do you select bearings for this application? I can throw the same bearing numbers, but the precision rolling shaft, operating in the zero vibration, with eccentric shaft movements in the sub micron/tenths world, there's some intellectual property here, and I've not seen a youtube channel that describes anything but the alignment of the matched precision pair to minimize runout.
Center of mass, and where that is, I think is what I paid for in the Dumore grinder. It needed new bearings, but they really needed a cleaning and oiling. The universal motor's rotor, had mega balancing grooves cut in the steel laminate rotor winding iron, in many place, it looked like they used a cutoff wheel. I was able to pry the metal dust shields off, wash and then re-oil the roller ball assemblies, which were just dried out from years of sitting unused. And that was on the motor bearings. So what is the game to make a perfectly balanced spindle, and select bearings that are not in the kilo local currency to purchase.
And I tried to make an extended spindle adapter to fit on my Czech made tool post grinder, got a pretty good match on the metric taper, but it has an extreme runout, so holding things between centers is not giving me the precision machining needed to make one long enough to grind the #4 Morse taper depth on my lathe's head stock adapter. I fixed the 90mm metric taper adapter's outside error. I referenced the Morse taper, by finding an odd adapter that I could hold between centers. In the end, I can't trust my tailstock to hold the correct center relative to the spindle, as I think it's another manufacturing defect of my lathe.