Originally Posted by RobbieTunes

I'd bet the Shimano 600 group, if it's tri-color, came on the bike. I'd bet the Tange Levin headset came on the bike, especially if it's black and actually says Tange Levin CD.

My 1989 Master Ironman has Shimano 600 tri-color; some call it Ultegra, with a Tange Levin headset.
My 1989 Expert Ironman has, as all '89's did, Suntour GPX components and a Tange Levin headset.
My 1988 Master Ironman has all Shimano 600 tri-color, including the headset.
My 1988 Carbon has all Shimano 600 tri-color, and the headset says "Centurion."
My 1986 Ironman has all Shimano 600 components.
I've tried several times for a Shimano 105 Ironman Expert. To date, no luck.
I've got time.

As far as the Maillad 500 hubs, not OEM on any Ironman, but decent hubs.
Your wheelset just doesn't appear OEM. No biggie, still a nice bike, and I'd love to have it.
Ride on.