While 120 hour movements became more the standard after WWII, not all were conversions. Both Mosler and Diebold made these as OEM, I have examples here: http://www.my-time-machines.net/mosler_34.htm, and here: http://www.my-time-machines.net/diebold_4_mvt_type3.htm .
A lot of conversions from OEM to the new Swiss movements are YUK! But a few were done with some finesse. Andy Kotas was one such converter who specialized in the conversion of S&G time locks that were made prior to their adoption of modular movements. Here is a page dedicated to his work: http://www.my-time-machines.net/sg_2_mvt_modified.htm. His style is recognizable and he numbered his work. I can’t say for sure, but I believe he was also authorized by insurers against lockouts, another testament to his work.
I’m sure there were others, and I have other examples of conversions, some better than others, but I collected them because they are an important factor in the history of time locks, keeping them relevant in the absence of a complete bolt rework as well as the fact that I’m simply a compulsive collector. 🙁-: