Let's say that the Spinks who fought Holmes instead fought a prime Eddie Machen. Could Spinks take him or would he be taken?
I think that prime Eddie Machen was a better boxer, he went 12 rounds with Sonny Liston in 1960, before losing by decision. Patterson avoided Eddie until 1964, Floyd beat him by decision. Machen would have had a little too much ring savvy for that version of Michael, Eddie by decision. It would look like a chess match though.
Machen wasn't better than Holmes in anyway. In fact, he's like a poor man's Holmes. He'd lose to Spinks clearly.