There was a thread the other day about how much input do you allow a customer to have ??
In this one, the flames must go the other way. I don't care if it's his logo and he has it everywhere else like that. It's 100% wrong going backwards like that on a vehicle. If he insists, tell him he has taste for chit and you'll do it, but you don't want anyone telling anyone else who did-done-doed it. It looks like a joke.
Like Jill said, on the back he should have a vertical flame. You can use the same color scheme, just make it look vehicular and not like a kid's coloring book.