Chris:

I just recalled that the spacer the diameter of a bearing is the lubrication ring, it goes at the front, but to be honest, I do not recall if it goes before or after the spacer washers; does the small washer have a step on the inside diameter? if it does, it is the compressor spacer, it goes in after the front bearing, before the compressor...If you do not get any help, let me know, I could disassemble my 280 over the weekend. For balancing you can go to an auto turbocharger shop, if they have a dynamic balancer they can do it for you, but you need to specify exactly where they can remove material from at the compressor and turbine wheels, and that the assembly needs to be balanced to less than one gram after it is assembled(complete turbine core minus external cover/compressor cover), if they won't do it this way it won't work...