Kona Mahuna 2013 headset change question.
The best place to find what headset you need is the Crane Creek headset finder.

Unfortunately in your particular case I thought the Mahuna has a straight 1 1/8 head tube and if so (correct me if I'm wrong) and therefore won't be able to take the tapered fork (easily, people have tried different things). Tapered steerers fit in tapered and 1.5 straight (with a reducing top headset) head tubes.