I mean, he died over a decade ago, so at this point the question is really just academic.

It certainly sounds like he was a true believer in the KKK in his youth.

He publically rejected them in his middle age. I'm not going to pretend that I know if it was cynically reading the political tea leaves or him honestly growing as a person.

I would just say that it's interesting to contrast what the NAACP said about Byrd when he died to what their chairman said about Strom Thurmond when he retired:

[Strom Thurmond] is a relic of America’s shameful past, who had long overstayed his welcome. And shame to his colleagues who confuse simple longevity with an illustrious legacy.

Good riddance.