Good info... thanks. This is looking harder than I thought it might be. The STX bottom cup bearings look to be caged. I have bits of an LX that I'm using too. I need to go back through everything and work out what I have and haven't got.Problem you’ll have is some Shimano headsets were cartridge bearing and some were caged ball bearings, so will need different races.
I think all cartridge races were the same at least.