Decent old bus. Like others, I wouldn't give 9k for it. Looks pretty rust free for the age in the pictures.
Could have a retarder on it. Dashboard shot shows some gauges and other add-ons on it that weren't standard options. Not sure if a retarder was law or not in CO, but they outlawed 2 speed rear ends in a lot of states because of the monarch pass accident that happened there. Retarders might have been just a commonly ordered option in the mountains after that. Cowlitz might have the answer to those questions.
Retarders are nice, but not needed if you're in the flats. It'd be like having air conditioning in the arctic.
466's are great, but if it's never had the liners and o-rings replaced, you can bet you'll end up having to do that if you buy this and try driving it for 30 hours against the governor.
Being a 1986 model, I highly doubt it's got highway gearing. Federal speed limit of that time was 55mph, so there's no reason to gear it any faster. Plus, you wouldn't want it geared for highway speeds being in the mountains. Could have a governor on it. It'd be a box that's mounted on the throttle cable between the pedal and injection pump. Removing it might gain you a few mph, but you're still very likely gear bound.