My immediate thought the moment I saw he became an automobile was that the punchline of this chapter would be one of those "dragon fucking cars" memes that got popular in Japan from the west. I'm kind of glad they didn't go there, but also, waste of opportunity I say!
The funny thing about this ending is that this could be a legit doujin in it's own right. Reincarnated as Truck-Kun himself.
It would be a comedy adventure isekai in the same vein as Vending Machine. Just a fun little road trip as he collects new party members and they enjoy his camper powers (he also gains new powers as he goes a long).