Bought a kx450f-12 trippleclamp set and had one kx125-90 set pressed out the stem of both of them...
Length is roughly the same, but where it counts, the bottom end of the stem the 1990 stem is 30,10 mm and the 450-2012 is 30,20 mm, so reusing the one from the 125 doesn´t seem like an option. Also thought about reusing the stem from the 450 and turn it down in the lathe, but not enough material to cut the new threads it seems.
Well gonna look into a machineshop to fix me up with a new stem and a bushing for the top clamp...