I've heard inter city buses make great conversions. There are a couple bus companies here that have routes which go to several cities. Namely between Salem and Portland, which is a 54mi drive. Sandy to Portland is a 42mi drive. So it really depends on which route the bus was on, which determines the motor and how it was maintained. Given that transit companies pick specific buses for specific routes.
"Courage is not the absence of fear. Many couragious people have been terrified out of their wits. They are just tired and can't take anymore" Cptn. 'Hawkeye' Pierce.