We looked at a lot of buses before we bought ours and I learned pretty fast that the rated capacity has little to do with length, but the number of windows don't lie
We have a 10 window 94" Conventional/Bluebird that gives us about 24' of building space behind the drivers seat rated at 54 passengers, looked at a lot of 11 window buses that were rated at 66 passengers that had about 26'. There were plenty of other buses mixed in there that didn't fit that mold, we drove 700 miles to look at a 65 passenger that turned out to be built on a 77 that had 30' behind the drivers seat. We didn't have a good side picture and I took the dealers word about being a "standard" 65 passenger bus. We found that most dealers have little time for a rec bus buyer.
Moral of my windy story, get good side pictures and count windows before driving all over hell and gone and don't put much stock in what the dealer/owner says about capacity as it relates to OAL. Dealers go off the manufacturers plate and private folks just don't really know. I was told all kinds of things that didn't make any sense, called a guy in Arizonia about a 9 window Amtran conventional sitting in his yard. I asked him about the available building space behind the seats, he told me just over 30'
Be patient, a bus is only a good deal if you get what you want the first go-around, there's not much about them that's cheap or easy to change after the money changes hands!