Like you I had thought 42 stayed with Mk.2s, but Joe Ashworth's book shows them having 3s from NOV65 - SEP 71, when they converted to Nimrods. It also shows 977 as being with 42 from MAY66 (post Viper fit) to MAY68.
I did 2 months in Majunga from 205 in summer 68, and a short detachment in Oct 69, with Boots as my co-pilot and Gerry "Primrose" Lane as Nav Captain