US Airways has been mixing up tail numbers lately so that makes it harder to tell which one is which. Just by looking at the ending two letter codes, one cannot tell 100% anymore which one is which. USA also has changed some tail numbers in order to be able to track the fleet better for TA deployement. Thus, all the A330s/76 and most 75 tail numbers were changed.
In the midst of changing the 75 tails they gave up, and just continued retrofitting 900 tail with winglets to be deployed to TA service. The west 75s were also supposed to be changed to 200some tails, but they did not follow through with that project. All 900 75s were to be non-etops designations under the combined tracking system, but I believe that once they wound up getting rid of all the non-etops 757-225s that once belonged to Eastern, they just stopped. Both east and west 757-225s were scrapped quickly getting rid of the need to keep a non-etops 75 fleet designator. Therefor the 75 fleet currently keeps a mix of 900 and 200 tail numbers. It would be neat if they would have continued with the project of making all etops capable aircraft 200 tails.
On the 320 family, A/C sporting IAE engines dubbed A3xx-x32 were and continue to be west metal, while GE sporting Airbus dubbed A3xx-x11, A3xx-x12 and A2xx-x14 were pre-merger US aircraft currently serving the east side of things. US Airways is currently only registering A/C under the tail numbers ending AY and UW. AW tail designations been discontinued post merger. I don't think that they are even assigning US tail codes anymore either.
The only way to distinguish clearly east vs west airbus narrow-bodys is by looking at the engine shape at the airport.