See if you can find a build sheet on it--there you can see if it was spec'd with oval tires from the factory...
But seriously, that sounds like a good deal to me. People have lots of opinions about the 8.2 but that's all they are. Those tires (if not oval) and the bus as scrap look worth the asking price alone.
If the engine and tranny feel strong, you cant go too far wrong. That shorter size is nice but I will say that all the short buses built on full size school bus platforms like yours have been verrrrrry bumpy. You can do things like air down your tires (not below mnfr's ratings though, just to what your axle weight is), ride with ballast, and modify your springs to help. If your shocks are spent it will make the bounces oscillate longer, but replacing them will generally not soften the ride, just make it more even
Patina enthusiast and professional busman