I think I may have got this one a couple of days ago but I answered it in the form of an edit to another post (near the bottom of page 11):

Quote Originally Posted by vambo25 View Post
And a bit of judicious Googling would suggest that the Route 66 location is Delgadillo's Snow Cap Drive-in in Seligman.
Sorry confusing things. Of course, I may yet be wrong; better men than I have been confident but wrong in recent days!

Peter