According to the information I could find, which wasn't very consistant, the Aerobus came standard with a V8 engine, no option for an inline 6. Where the sources have a descrepancy is what V8 was used. One site claims Chevrolet smallblock, but the other shows a Chrysler 318, and has an oriiginal spec chart to prove it.
I'm inclined to think that the engine you have was not original to the car, and just based on the description, it is most likely a Ford, but i would not rule out AMC either. The center bolt rocker cover rules out Chevrolet.
Do you have a pic?
