The common non-factory update to a LE no-dash 66 was the removal of the trigger stop from the frame. Generally the department armorer or another LE approved individual did it. Most LE agencies get cranky, even to this day, if a non-LE approved change is made to a service pistol. That applies double if the gun is agency owned.
Some smaller agencies can be more lax. However if the gun goes to the academy with a new officer in training, most will get a serious evaluation by a trained armorer. Non-spec parts get tossed in the eval process.
That said, in my "shooter" early 66, the serrated trigger was removed and replaced with a .312 wide factory smooth trigger. Much better for DA shooting.