I lived in the Phoenix area for 12 years and never seen Rudolph license plate rings (not saying they do not exist) Rudolph had a decal placed in the center of the trunk lid usally below the trunk lock. It was usally black in color and said R U D O L P H w/ a smaller PHOENIX below it in capital letters and the color of car showed through all the letters. Not sure what they used on Black and dark Blue colors. I owned a low mileage 1972 Impala with the Mulsanne Light Blue and my friend had a White 1964 Malibu SS that had the black decals. Rudolph Chevrolet was big in HP Chevrolets and drag racing in the Phoenix area and was one of the original Phoenix area Chevrolet
dealerships. They went out of business in the mid to late 70s. A note of trivia One of Rudolphs daughters married Lou Grubb who started Lou Grubb Chevrolet shortly after Rudolph went out of business. Maybe they have some of the old Rudolph decals, Its worth a try. My brother was doing renovations on a old house and found a 1966 RUDOLPH full page newspaper ad in the walls that showed a top view of a 425Hp 427 with a picture of a Corvette, Biscayne and SS396 Chevelle below it and the ad said DO NOT TEASE. someday I will unpack and post this cool ad.