Shadow Shot Sunday - Mesa mystery

Three well-dressed gentlemen in front of a mesa in the Grand Canyon State, (1937?)

License plate mystery solved?

 Shadow Shot Sunday 2 and my namesake grandfather - it's not necessarily new for me as I have been chronicling the distant family past for awhile now (as Patti knows :). Yet my father's sole sibling, Aunt Terry has been following these photo memes and sent me another box of old photos a couple of weeks ago full of photos I haven't yet seen...
Always interesting is not knowing the background of the shot at all - so I merely guess. 

The three gentlemen, Grandpa in the middle, are obviously on the way to someplace special since they are wearing nicely tailored suits - in the desert? Maybe this is on U.S. 60 west from New Mexico?

More interesting are the two license plats on the car. his usual Ohio 'RV' plate and another - his radio license? The second photo, taken in 1977 or 1978, may explain that - the 1937 Ohio tag and...the 1937 radio license? I cannot say - however, along with the shadows, I do like a mystery...