4th & 5th. That's what the senior mech at Russelville told me.
Overdrive: When the system "output shaft" is spinning faster than the "input shaft."
Overdrive on a VTwin transmission and overdrive on a shaft drive transmission are VERY different animals because on a shaft drive bike, there is another gearbox (rear end differential) to lower the RPMs.
Whereas on a typical VTwin design, that transmission output shaft is spinning the belt to the rear wheel.
Hope this helps,
Steve