56picup,
Without the governor to complete the electrical circuit, I don't think the overdrive will engage. One thing you need to be careful of though is the freewheeling part of the overdrive.
If you have the cable pushed in, the freewheeling clutch is enabled and the vehicle will freewheel if you back off on the gas. When parked, it will also roll forward if you don't put the gear shift in reverse. There is a lockout that disables free wheeling when in reverse. So run with the O/D cable pulled out or make darn sure you put it in reverse when you park. Otherwise it might not be there when you come back
