Olefin here's something else for you to have a peek at, as mentioned by Raellus, Argentina did produce some of its own armour but they also had a large quantity of tanks that were surplus to requirements after they got the TAM into service.
While they probably tried to dispose of them in the normal manner they didn't succeed and they were still in Argentina as of 2002. These tanks are Shermans, they had about 450 initially and then upgraded 250 of them with more modern engines and other systems but also with... a 105mm main gun.
They remained in service until 1994, probably too late for a version 1 timeline but kinda about the right time for v2.
This article gives a lot more detail
https://www.warhistoryonline.com/war...tell-us.html/3
Now that would be a hell of a surprise, the X1 light tanks and the Sherman Repotenciado mediums as the basis for a battle group. That 105mm would give the Mexicans some hitting power without the unbelievable totally Soviet armoured force proposed by City of Angels.