I added …
Farmer in the Sky, Heinlein – 1951 (Awarded in 2001)
The Mule (Part/Book II of Foundation and Empire), Asimov – 1946 (Awarded in 1996)
It seemed unfair to have Fahrenheit 451 as the only retro award winner. It was written in 1954 but awarded in 2004. I know the Retrospective Hugo’s often cause a bit of debate. But hey, what’s an award without a little drama?
An alternative that may appease those who think judging books 50 years or more, after the fact, isn’t truly keeping with the Hugo Award’s spirit, would be to add the three books in their own list and maybe provide a link at the top of the description here for relation.