Unit (vehicle) upgrades in campaign game

[MOTW]

Hello all! First let me say how excited I am to have found this game! Excellent remake of an all-time classic.
I like the new expanded list of swappable vehicle types; tanks can be changed to Gunships or transport Helos, S.-P. artillery types can become a great many things also, but for some reason when something becomes a transport vehicle, it is stuck and won't be able to change in to anything else. Whether truck, wheeled or tracked APCs, scout vehicles or other related items, once they are in that class, it's over. I seem to recall in the original S.P.2 being able to upgrade APCs (sometimes trucks or jeeps) to transport helos. (I've noticed helo classes can become APCs, but then not change back) So my question is this: where might I find a list of what classes can be changed to other classes (if such a list exists)? If not that is there something that can be edited so I would be able to change a wheeled or tracked APC into a helicopter; maybe also change a Scout vehicle or armored car in to a FO vehicle? Any help or guidance would be much appreciated.