I disagree. They are noisy, huge, and energy inefficient. If you're going to rebuild it as a bus to haul people in, by all means, keep them. Otherwise though I can almost promise you that you'll need another heat source (can't keep the bus running all night).
What I WOULD have done had I had the patience is scrap them all and then used the hookup to lay down radiant floor heating with pex tubing using the same basic idea. If you hook up a propane boiler to that you've got a toasty floor.
But yeah, I say scrap them. Put two hefty 12v defrosters/heaters up front if you need them.
Roads? Where we're going, we don't need ... roads.