I need to make a correction here.
It is the rear gearbox bolt that is too short. The one with the adjuster on it.
There is about 8mm difference in the length of the two bolts. Enough to get a serrated washer on the longer one but not enough on the shorter one.
If you want to use the short one in combination with a serrated washer you could adapt it by taking a few mm of the thick part of the bolt and file the flats a bit further. And take the same of the distance piece so that you have more threads sticking out.
As result you may also have to file the fork which take the adjuster a bit deeper. This brings the adjuster a bit closer to the mudguard but there is usually enough room for it.
But it a bit of a shame to adapt such a nice looking bolt...:slightly_smiling_face: