Rear axel changeover

[chev49]

i suppose you mean a FE bus and flip the axle, or do ya mean a RE one and just change it out from the school bus. esp in a school bus, you gotta check the gear ratio as many of them are the 55mph busses which isnt the ratio you want...
newer truck rear end flipped is what i would prob do, but my bus will go 73 or so and wife hates me driving over 60...

[TomC]

Yes

[Oonrahnjay]

(snip)  my bus will go 73 or so and wife hates me driving over 60... 

     Yes, but if my bus will "do" 80 with my foot on the floor and it's "best fuel economy" is about 60, that's where I'll run and set the cruise most of the time.  Your rear axle and your overall gearing mean a number of different things.