Updating this thread to help out future google searchers -

I have this bike and after 40,000mi the headset was getting a lot of play and had a a lot of wear and brinelling on the races. I found the same bearing cage and pressed in headset cups which also surprised me.
If you remove the headset cups, underneath is a beautiful machined 45 degree surface that accepts Cane Creek style integrated bearings. I measured the headtube as 42/52 mm and ordered a Chris King Dropset 2 headset. It fits perfectly and works great.