I don't know Alan. Pearson used a bunch of different designers other than Carl Alberg in the 60's. Bill Tripp designed the Invicta centerboard ketch in 1960, Phil Rhodes did the Rhodes-41, and John Alden the Countess 44 ketch in 1965, all built by Pearson. Bill Shaw, promoted to head designer, did a bunch of designs for Pearson too.
The Shaw designed, Pearson built, Lark 24 had a flush deck, ala Lapworth's Cal 28, in 1968. The Pearson 22, by Shaw, was almost a copy of the Santana-22 by G.Mull, complete with fin keel and spade rudder. And the Pearson 33 and 35's in the late 60's, also by Bill Shaw, had centerboards.
With this smorgasboard, I'm gonna choose the Lark 24 as the answer to your quiz. It was late 60's, full keel like Alberg's Triton, but different with the flush deck.