current gear ratio:
5.38 yields 65 mph
if the engine has enough hp, top speed would be increased to
78mph with a 4.44 ratio
85mph with a 4.11 ratio.
more important than speed (realistically, who's gonna go 75 mph in a skoolbus? you'd have to be a crazy madman!) is lowered rpm for a given speed thus increasing fuel economy (in theory) and decreasing wear and tear on the motor.
65mph currently = 2,700 rpm
4.44 ratio would = 2,133 rpm
4.10 ratio would = 1,863 rpm
(i think i calculated the rpm figures correctly)
The 4.10 ratio might be a little too conservative, I think i'll aim for a 4.44 rear.
Quis custodiet ipsos custodes (who will watch the watchmen?)