Road wheels 4.5 on 5 were available from 1970 on.
http://imperialclub.org/Repair/Wheels/covers.htm
The Imperial club shows them first being available in 76, interesting
Up to and including 1973.....Imps were 5 on 5 wheels.... weren't they?
I have a friend who's grandpa passed, and they are selling his 74' Imperial. He bought it new. If anyone Is Interested I can get a price. It's green, of course.That's because the Imperial site only caters to Imperials and recognizing the 76-78 NYB, because the Imperial existed until 75.