mtb headset question

[fuddam]

I have a bike from 1997. It's a custom bike - frame custom built by Columbus with 0.4mm cromo tubing - and is fitted out with pretty much all Shimano XTR components, and a Rockshox Magnesium fork. The headset threading recently got stripped, and I obviously needed to replace it. It's a threaded headset, and removing the cups is all but impossible. The threading on the steerer is still fine.

It looks like there is threading on the lower edge of the upper cup, which I've never seen before, but I'm ignorant. That threading is completely stripped, if that is what it is.

The fork steerer outer diameter is 28mm
The upper cup outer diameter looks to be 1.25 inches

I'm trying to find a replacement. Any suggestions?

Also, I assume I can't simply replace the threaded headset with a threadless design?

If necessary, I can post pics.

[KowShak]

Threaded headsets are fairly standard things...

How does your headset compare with this type?

The headset cups are usually removable, you can remove them with a hammer and chisel if you're careful but there are proper tools too...