Ok looked through my few pictures of 71-73's and its often difficult to see the buck tags as they can be hard to see given the camera angles and other things that get in the way
My finds follow along with the feedback you got from the members of the other site so I guess whomever you talked to at a show was misinformed or had only seen a limited number of examples.
I found that all of the 71 Dearborn cars had them located on the passenger side of the radiator support. In the pictures I have there appears to have been two possible locations but both are within inches of the other but both near the upper edge of the support.
For 72-73 they are located on the drivers side of the radiator support near to top edge. All appear to be in about the same locations