Re: Bus (diesel) end of the tail pipe, how hot?
a piece of sheet metal used as a "heat shield" would prob be the simplest.
another option is just cutting your exhaust off closer to the front of the bus. I cut the exhaust off of a previous bus. I took one of the elbows, cut it off, and welded it on the tip to help point the exhaust down and out the side of the bus in front of the axle.
a bus doesn't really need 37 feet of exhaust tubing.
Quis custodiet ipsos custodes (who will watch the watchmen?)