Tranny swap Questions

[Naked Buell]

So I have a newer jdm 4-11 5 speed and its going into an older case to be able to use the cable clutch. But I think I prefer 3.9 gears so I am not doing 3500 rpm at 70mph.
My question is, can I just change the ring in the tranny as I am swapping guts??? Do I need the pinion gear that goes with the 3.9???
Please advise.
Thx guys

[Legacy777]

I would recommend swapping both the ring & pinion since they will have worn together evenly. If you swap a different pinion and ring set that have worn differently, that may cause issues. I can't say for sure, but maybe someone else will chime in.

You'll also need to set shims and proper backlash when changing gears in a different case.