Happily the data I thought was normals turned out to be normals, which you can see rendered here. They’re most obviously used to show reflections on the cars.
Each car has the hi-def model made of 25 individual parts, and three LoD models, in addition to 4 wheels and a few other entries with <3 vertices. Not sure if those are used for something or just dummy data.
I haven’t really looked at the wheel data yet, at the moment they’re displaying with the texture only covering half of the wheel, I guess the bottom half is meant to be a mirror of the top but I have to find out what causes this (or is it hard-coded? wheel textures have their own table).
Still no idea how a given model/texture is assigned a palette, and I feel like there might be a problem with the palettes I’m inserting, for one model I’ve noticed the palette doesn’t seem to match the in-game one anymore.