Someone is making/made repop shafts with 5/16BSW or 5/16UNC (hard to tell). I did not buy them. Wish I knew who, so I could tell.
bad bad bad
They are hardened... since I can not chase the threads to make a screw go in with out eating the thread up.
Genuine are 26CEI thread.
So don't be surprised if you find some.
added:
Contribution from NOC site by K. Glassborow
These are apparently from Les Harris Spares, the former 'new' Triumph builder in the 80's.