Unit 012: M41A3
Unit 014: M48A3
I would suggest providing a vision 0 version of both units. While the M41 in US service featured as standard a visual light searchlight on top of the main gun, this appears to have no been common in Vietnam. Most of the images show it without this unit fitted (Seeing the gallery I linked in my initial post or any of the sources mentioned).
The version with vision 10 (Unit 012) should remain in the OOB, however, as while uncommon it did exist. There is a picture of one with the visual searchlight fitted on page 14 in Osprey's
Vietnam Marines, 1965-1973. The tank troop TOE of 1966 only authorized 7 searchlights in total per troop, with 1 in the maintenance section and 2 in each of the 3 platoons. In my ARVN OOB, I created a separate tank type for the searchlight equipped units to recreate this.
In addition, a vision 15-20 version should also be included with a start date of 9/66. This represents the mounting of the Xenon searchlight found on the M48A3 to the M41A3 tank first in 9/66. The potential use of 15 rather than 20 would represent that these vehicles were not equipped with IR sights, and therefore only the commander with IR binoculars could make use of the night vision capability, degrading its overall effectiveness. It appears this was very rare, so an X1 radio code (or maybe even an X3 radio code) should be used. Really this is probably a debatable entry because its unclear how many conversions were made.
Similarly, the M48A3s supplied appeared to also have been largely without their searchlights. While it is also clear that the variant with the Xenon light (unit 014) was used, I would suggest adding in a vision 0 variant.