Have you ever hauled ducks? they are far worse than chickens when it comes to stinking up a car!Haha. It actually wasn't too bad.
When I haul chickens in vechicle (not truck beds) I leave the doors open for a little while and let air full through italways the practical considerations. How does one get that smell out anyway? It stayed in our basement for quite a while after we moved the chicks out and cleaned everything.