fenders...planet bike has clamp on fenders for road bikes, I like them better than the "full" fenders, less rattle.

rack... get one that can clamp to your seat post (I have one, and they work great, even with a loaded bag attached - don't remember the brand).
This morning I attached a standard rack to my 86 lemans (58cm), and my foot was hitting the pannier all the way to work.

wheels, I've used 28's on my lemans with no clearance issues (but I only run a front brake)

This is all assuming that the ironman and lemans have similar geometry/sizes....