ATI will not sell *ANY* headunit service parts to the end user other than drain plug o-rings and dipstick seals-- I did call and ask although I did not get pushy nor would I have. They will only perform service on the units and replace what is needed and tell you to send the thing into them for inspection/service.
On one hand I can see their point-- if someone botches an install using parts they sold that guy might come whining back to them wanting to get it repaired/replaced for free. But for a guy like me who is out of warranty I don't really see the harm. If I screw up it's on me and I'll pay to fix or replace it. Let's face it, this isn't rocket science to rebuild one of these things but you can screw up the bearings by being overzealous or stupid with the press. The rebuilding thing is probably a cash cow for them too, if I had all the parts in hand up front I could knock it out VERY quickly and for what they charge I'm sure the profit is pretty darn good.
There are better bearings out there than what they used in my build but I'm guessing it boils down to a cost thing for them. As I mentioned earlier if you run the headunit at ATI's advertised maximum speeds you will be exceeding the manufacturer's spec for both the low and high speed bearings.
Not to mention the bearings on the oil aereator gear say "China"
My plan down the road is to change over to ceramic GMN bearings on the high speed side as they are rated to 78K rpm. The low speed side currently uses 11K rpm rated Koyo bearings (keep in mind at a max impeller speed the low speed bearings will see 15K RPM, so ATI is once again overdoing things a bit) and there are better higher speed rated alternatives for there as well. I have not priced them out but I'm sure they will be more expensive than the bearings currently used-- how much more I don't know.