Remembering that by '81, Pagewood (H) was closing, which left only 3 plants - Dandenong (J), Acacia Ridge (H) and Elizabeth (L).

Commodores were made alongside WBs at Elizabeth in the '80s, you can roughly guess the date from the tag numbers of other cars built in the same plant, in the same period.

Based on commodores I have recorded, L522xxx falls within a 6 week window between the start of June to mid July 1981 - probably more likely to be June.

--- Updated ---

ADR 27B didn't come in until 1/82, so this WB still comes under 27A.

However, don't discount ADR72B - I have recorded VC commodores from 1981 - as early as March 81, that have 27B stamped on the plate, but these were NSW emissions cars.