Badge loyalty happened a lot! I worked for a BMC dealership back when the commercials were still badged as ‘Austin’ and ‘Morris’ (we sold Morris) and customers wanting a vehicle that we were unable to supply from stock would rather wait a month or more than go a mile across town to the ‘rival’ Austin dealership where they had stock! Vice versa applied of course. Identical vehicles apart from a plastic grille badge but old loyalties meant a lot to operators back then.
Regarding the comment about the armed forces struggling for parts etc overseas, my dad was serving with the army in North Africa from 1948-51 and he said that when they needed a part for a vehicle that wasn’t ‘in stock’ they could usually buy some back from the Arabs who had stripped the vehicles etc left abandoned in the desert during WW2! 
Pete.