Custom made, machine steel and hardened splines. In Australia the number of five speed cars is quite low (well under 250 cars imported across the country) and in the 90's people were wanting to fit five speed transmissions to their X19's ... importing a transmission not so hard... axles/hubs/c.v's adds a heap of weight to the package... so the idea was hatched to make axles with spline / size on one end to fit the five speed inner CV, and the other end a spline / size to suit the outboard CV joint of the four speed, and this is the last set of axles I have left... the other sets all sold / were fitted to cars.
Kevin, for you in the states, it would be easier to source the five speed specific parts.
SteveC