I don't claim in any way to be any kind of authority on his auto.
I know that the Pro-Line autos should have a embossed mark on the card that it is an "authentic signature".
I've seen a few items pop up that were framed photos with a cut signature framed along with the photo, but those can be "facsimile" signatures, and that is not always listed honestly.
If you've been exploring, You've no doubt noticed how his autograph degraded as he aged, and the Parkinson's, along with the other traumas he endured through his boxing career, took a toll on him.
I've heard stories about his final years, when he was in poor health, that his family would try setting up "autograph sessions" with different dealers. I've heard some things from those signings that would personally steer me far away from those items.
Me personally, I'd spend the money on a earlier signature, authenticated by a reputable party.
As said, this is my personal thoughts.