Could be anything. Starcraft, Eldorado, US Bus, Goshen, Krystal, etc. Then among them any of many many hundreds of models with all different window and door configurations, lengths, etc. The upfitters pretty much build them to a customers specs as far as options go. They usually are one of several standard sizes. But there are so many option that can change things up. Starcraft for example - two different rear caps (one sort of flat the other heavily inset), may or may not have a window on the rear, they install wheelchair lifts in random places (sometimes in the rear, sometimes toward the front on the side, sometimes towards the back). Some might have that window cut in above the windshield, some might not.... etc etc.
We have done many dozens and it seems they almost all have slight differences. Two should be identical buses side by side, on one the windows are all installed an inch higher than the other. Bubba cut the windows in on that one, Bobby cut them in on that other one.... I see it a lot on Ambulances as well.
Best to not do much until you can personally get photos and verify the measurements of the actual bus.