The only real difference in latch assemblies is how they function. The '65-'66 latch assembly locks only with the exterior key or, with the door closed, via the push-button lock.

The Kaba Simplex solves the problem because it is a mechanical lock that utilizes push-buttons, which, believe it or not, are allowed under Jewish law.

A Simple Approach to Fabricating Push-Button Door Handles for a kustom 1962 Mercury Comet.