Ross wrote:
Beautiful car. Take a little care as there is something amiss with your overdrive. There should be no need to do anything to make the car back up other than put the car in reverse and let out the clutch. That is true whether the knob is in or out

It seems that your overdrive is staying engaged even at a stop which tells me that it is wired up wrong or the governor, which tells the OD when to become available, is stuck "on".

Get a little more experience with the car and let us know what it is doing. If the OD continues to give you fits just remove its fuse till its figured out. OD is a very valuable feature as it makes the car easily capable of highway speeds.