I went to my local bike shop today. They had an Aheadset brand (Cane Creek's cheap line I think) 1" threadless that is, I think, full ISO (30.2 mm cups and 26.4 mm races). Model TR.1. In this one, the crown race and head race are actually identical, and they have a special compression ring/seal at the top. Eh...it's what they had so I tried it. They installed it for me. The cups are actually slightly stepped, and Aheadset's installation instructions says that the head tube needs to be 29.9 mm. Okay...that's what I have -- and I thought that was JIS. But the cups on this are 30.2 mm. Whatever.

http://www.aheadset.com/downloads/AH...structions.pdf

AHEADSET :: Bicycle Headset Manufacturers

You can see that the webpage confirms that the cups are 30.2 mm. And the PDF instructions say your tube can be 29.9 mm. Weird.

He did have a hard time getting the top cup in and said it was due to paint over spray in the head tube. He had a ball hone on a drill and used that to clean up the inside of the head tube. He then greased the head tube and the cups appeared to go in without too much trouble. That just left the crown race for me to deal with. I filed the 27.0 mm crown race seat on the fork down to about 26.4 mm and seated the crown race at home.

I think it's gonna work. I do not have a jig to cut the steerer (but the bike shop does, so I'll probably take it to them to cut and face it next week). Then I'll paint and install it.

I'm left just a touch confused with Aheadset's documentation on this headset. It seems to say that their 30.2 mm cups will work in 29.9 mm head tubes, which goes against a lot of what I've read. Maybe they have that "stepped" cup design to accommodate both standards. It seems like it's going to work for me. In the future, if I need to replace this thing, I guess I'll be able to use a standard ISO headset. And my fork is now ground down to 26.4 mm as well, so I'm good to go there.

Thanks, all, for the help.