These all have the same later gearset/bearing designs. All have too tall of gears on 3rd/4th/and 5th 1.23/.95/.76).
Changing any of them requires accurate machining and welding to fit the revised internal design.
Re-hardening is critical and afterwards the cluster gear has to be opened again to fit over the shaft. Thats just a result of heating and chilling in quenching oil.