Were the pan holes straightened before being reinstalled? I place the pan edge (facing right side up) along an anvil and use a ball peen hammer (ball down) at each hole--then give the B-P-H a whack to force the usually bulging opening down. Previous over tightening causes each hole to distort--then when reinstalled without correction the bulge bottoms out leaving the gasket unevenly tightened.
As for the tailshaft being a source of leakage---very late AW70/71 transmissions use a bearing instead of a bushing at the output shaft (I don't recall the year of change) but the earlier bushings do wear in the tailshaft housing--there should be no play at the output flange. Bushing/seal replacement is an easy fix. -- Dave