We've been using the Chevy diesel chassis for quite awhile and I'm sure we could have stuck with it. There must have been another motivation for diesel. I'm actually kinda looking forward to the better pick-up and quieter engine. We don't have SSM, so it's not like the trucks need to sit idling for extended periods.
Otherwise from my poking around inside one of the unlocked ones, there's no major differences I can find in the trucks. Other than the odd addition of a CD player to the stereo and a different placement for our traffic director.
I'm fairly certain the livery's (once they apply it anyways) not going to change either since our current set-up is the product of a consultation with Dr. Levick.