We are talking about damage to vehicle's health, not to vehicle's mesh.
Most of the stuff is done. What's left to do:
multiplayer: Some wheels are not visible to new clients. Only the wheel from the mesh is visible.
inflict damage to vehicle on collision
detect petrolcap hit (too complicated, and not a priority now). 2 approaches:
detect hit on chassis mesh, and check distance from petrolcap - not possible because chassis mesh is usually one-sided, so we can't even detect the hit
create box collider on the place of petrolcap - this is difficult, can't remember why right now
We are talking about damage to vehicle's health, not to vehicle's mesh.
Most of the stuff is done. What's left to do: