http://www.bikeforums.net/showthread.php?t=480705
some posts there about Centurions.
I'm not sure that Ironman came with indexed shifting.
I have the same size, color, and it's friction Shimano 600, so someone may have upgraded.
Fit is the most important.
After that, I kind of like Centurions, and I'd go for the Ironman.