I am sure it can be done, however I think the hassle is more, than just keeping an eye out for a MPH
one and then having to possibly recalibrate? Not sure but someone in the know will be along soon to help.
They tend to come along now and then and the wanted section works a treat.
I have a few spare mph speedos. Take out the dash and carefully label all the wires (masking tape and pen) before disconnecting them. Dismantle and take out kph speedo and replace with mph speedo. What year is your bus?