John,
Sorry if I spoiled your fun. I had an Onan air cooled and the vibration and noise drove me nuts.
The EV6010 is made for RVs, it fits into the 4104 AC engine compartment very nicely but even so there isn't a lot of extra space, it takes in all cooling air at the side of the bus and exhausts it all out the bottom. My bay has an open bottom so it is ideal if yours is the same. Water cooled is inherently quieter.
It is flat rated to 6KW.
One other thing, it has a remote control, almost essential in a bus.
This makes one nice installation, quiet and NO vibration. After all I had read about 3600rpm generators I thought this would be noisy but it is half the noise of my old 1800 rpm air cooled Onan.
I think I paid $4200 for the gen, exhaust/muffler and remote kits. You also have to build a box. I used insulated plywood even though Honda recommends metal.