Richard is right, putting ACBs in there doesn’t sound like money well spent. Switching to an ACB will give you higher speed capability, but it is less rigid than a TRB of equivalent size, so you might end up with worse performance. The same size ACB also has about half the load capability of the TRB it was designed for, so your life is going to be significantly less unless you run at much lower loads. To get an advantage from the angular contact bearings, you would need to go bigger.
Another issue to consider, most angular contact bearings have a contact angle of 40 degrees and are meant for high axial loads, TRBs are in the 10 to 20 range depending on size and design as a comparison. You would want a spindle bearing in a milling operation that have either 15 or 25 degree contact angle to better handle the radial loads. Not much of a selection of those in P5, usually they are P4 and $$$.