Round Robin between the three title winning Alis ?

I think the 1978 version wins.

He's lose 11 of the 15 rounds but get a split decision.

 

I can't see 78 Ali being stopped in just 5 rounds. A near prime Larry Holmes couldn't even get him off his feet and he probably hits harder and sat down his punches more than a 64 Clay. However the end result of a 64 Clay victory is inevitable. I also like 64 Clay over 74 Ali. I just think he's too quick and can get in and out without being countered and can coast to a fairly comfortable UD. Ali from the FOTC Vs 64-67 Clay would be the only mythical matchup I'd be interested in.