Well, I'll go along with the revised date-- given the nature of the patter between the Klugmans and Allen, it's pretty obvious that this was one of their first appearances on the show, which means it has to be December of 1971. The halfway reference to the recent "Odd Couple" Password ep, and Allen's stumbling intro of Dr. Stockwell would all seem to bear that out, too.
My apologies for the initial incorrect dating-- I had been checking the ABC Password pages as well, and somehow just managed to thoroughly miss the December '71 appearance by Jack & Brett.
-Kevin