Perhaps this will be of value so someone in search of their OBD plug. I have a Ford F-53 chassis and there is a plug of some sort behind the front grill next to the firewall on the drivers side. When we purchased our motor home, this plug was in an upright position and I turned it so it pointed down so it would not collect water. I noticed it was a plug, can't remember whether it was male or female, and assumed it was for engine diagnostics but have never had the ocassion us use it. You might look in this area, if you are trying to find your OBD plug. I have been under my dash many times and do not remember seeing any sort of a plug which I thought might be for the OBD reader, but I have never looked specifically for that plug.
Richard