C. Noel: I have tried to cross reference unit locations by APO numbers, too.I have not been able to come up with either of the publications listed below locally here in Fairbanks, AK.Maybe you'll have better luck where you are.
Numerical listing of APO's : January 1942-November 1947 / prepared by Army Postal Service and Strength Accounting Branches, AGO. Title (1949)
Available Location: Ctr-Military History: General Collection / UH 83 .N9 1949?
Cosentini and Gruenzner (eds.), United States Numbered Military Post Offices, Assignments and Locations, 1941-1994, published by the Military Postal History Society, 1994.
I would be interested to hear if you come up with anything.