I have been researching the units that my father and an uncle served during WWII. These were the 762nd AAA gun Battalion, and the 766th AAA Gun Battalion.
I have a copy of the history of the 762nd AAA Gun Battalion, and a copy of the history of the 891st AAA Gun Battalion. In both histories, it is stated that "continental soldiers will be replaced by drafted Puerto Ricans" and that "the antiaircraft defense of the Panama Canal will be left to drafted Puerto Ricans." This change did not happen completely, as in those AAA battalions that were left in Panama after 1943, a certain number of "continentals" to use the words the histories use had to stay to train and serve as cadre for those Puerto Ricans serving in those units.
The following battalions were established from regiments when the pre-1943 regiments were broken up, and another resource available from the Institute of Military History states the battalions below were to receive drafted Puerto Ricans to replace American soldiers serving in them:
761st AAA Gun Battalion 762nd AAA Gun Battalion (formed from 1st Battalion, 72nd CA (AA) regiment; 1st Battalion, 82nd CA (AA) regiment; and 1st Battalion, 88th CA (AA) regiment) 763rd AAA Gun Battalion 764th AAA Gun Battalion 765th AAA Gun Battalion (formed from 1st Battalion, 73rd CA (AA) regiment) 766th AAA Gun Battalion 767th AAA Gun Battalion 891st AAA Gun Battalion (formed from 1st Battalion, 615th CA (AA))