In my quest to find one 390 may 1st 1970 rallye wheel (with no luck) I picked up a pair of august 12th 1969 15x7 wheels with original polyglas august 1969 tires still on them. My question is... I can't find the 390 part number anywhere. Are the early wheels stamp somewhere other than valve stem? Not sure how to post pics on this site anymore. Any help would be great