I think what you will find is the vehicle will be basically speed limited if you don't exceed the redline mark. The RPM of the gearbox gears is unaffected by the downstream reduction, so its automatic. For example, if i drove on the redline in high range in 5th gear, the gearbox would be spinning at the same rpm as in low range but the transfer reduction will limit the final speed, hence the sticker on the door is more to get people to concentrate on speed rather than RPM as its probably safer that way, I am guessing now.
So for us, in the bush, fitted with reduction gears, its more about rpm than speed as you are going to be crawling around like a slug anyway, even if you are revving its head off.