I don't know late Muhammad Alis enough to give an opinion on yours. But I would only buy an Ali from the last 5 years from a signing witnessed by a well-known and respected firm. Be it, say, Upper Deck or Steiner, which have signed for their own sales; or a private signing witnessed by a respected independent third party such as PSA/DNA or JSA.
Anything else would likely always be in question--his signature is simply too crude now.
If an index card is what you want, that's fine. But I don't recall seeing late Muhammad Alis from private signings that weren't on photos, art or memorabilia. Are yours from a private signing or something unequivocally verifiable? I'm just worried that even if they're legit, you'll have a hard time selling them in the future.
Thanks. Let's see your Michael Jackson's! He's a regular topic of conversation here. We have a stimulating conversation going on right now about a MJ that was being offered on eBay for $500,000.