According to Stanton's "WW II Order of Battle, your dad's unit, 503rd CA BN, was activated 7 Apr 42, at Fort Lewis, WA.
503rd CA BN:
Departed Seattle P/E, 22 June 42; arrived at Fort Glenn, Alaska, 29 Jun 42; Hdqrs BN inactivated, 30 Dec 43; 1st and 2nd BNs redesignated 95th AAA Gun and 594th AAA Auto-weapons BNs, respectively; 3rd BN was deactivated same date(?), 8 Feb 44.
CAMPAIGN: Aleutian Islands, 2 June 42 / 25 Aug 43.
95th AAA BN:
Activated Alaska, 8 Feb 44(from 1st CA BN, 503rd CA BN; arrived S P/E, 4 Jun 44; inactivated at Camp Maxey, TX, 24 Dec 44.
594th AAA BN:
Activated at Fort Glenn, AK, 8 Feb 44, from 2nd BN, 503rd CA BN; arrvd. S P/E, 6 Aug 44;'inactivated at Camp Livingston, LA, 1 Dec 44.
As the 503rd CA BN, possibly participated in assault on Adak Island, 13 Aug 43, where it was discovered that the Japanese had abandoned the island positions day/s before.
Neither of the above named units had ETO or Pacific duty.
I hope this helps.
Please let me know if it fits the profile you have developed. OK ?