I am excited for you both, what a beautiful bus.
I got a 80s GMC with the same 366 motor by choice.
I wanted a gas motor because it is familiar to me. I have been working on the common v8 for years, and parts are relatively inexpensive for these.
Mine does 65 on the highway no problem. I have a friend who is a motor guy and he said this motor was used is lots of tractors, bus, and dump trucks and that if the oil is kept changed often that it would last forever (a common thing to say about a motor)
It was new news to me that these, like diesel motors, are high torque low rpm motors. What this means is that they operate in the 2500 to 3k rpm range max, where as regular V8 motors go qiite a bit higher than that (5k and higher)
Pretty neat motor in that is has 3 piston rings (most have two)
also i love that V8 motor sound.
These really can't fairly be compared to diesel motors, diesel motors are superb motors too, but i thought i would share my fondness for the big block chevy 366.