The pre-Novak and Novak cut is the same but you are correct that the rear of the slide will need to be machined. You may find that you need to change the front sight also as the current sight will probably be too short for the Novak rear sight.

The Novak rear sight part number is 107920000.
The set screw part number is 108010000.
The front sight part number is 109090000.