Sweet heater! At first glance I thought it was glorified salamander style diesel heater, but I then saw it has an exhaust stack. Very nice. That thing would be nice for us folk during the truly cold winter months. It'd bring the bus from below freezing to comfortable quickly.
As far as BTUs go, the drivers side heater in my bus is rated at 80,000 BTU. I also added a small heater core and fan which points down at my lady's feet, but the bus heater does 95% of the work while going down the road. It has never had a problem keeping up. Even when it's been -30c outside. There were two other stock heaters (40,000 BTU and 60,000 BTU, if I'm remembering correctly), but I removed them.