If you have enough property to have a truck dedicated to specifically maintaining it, why can't you move the cars somewhere where she can't see them? Out of sight, out of mind.
I bought a rabbit off a guy up in NH once who had this wonderful piece of property around his house, about 5 acres out of 20, but over a knoll beyond some trees, he must have had 15 or 20 fire trucks sitting up there among other things. He told me that his wife could not care less as long as they were not visible from the road or the house. That was the deal he struck when they were married, especially since, unlike a lot of people, he was mostly interested in collecting extremely large, old municipal and emergency vehicles for some reason.
Pretty neat though, he had a city bus from the 20s and some other historical stuff