For all the cross beams and gunnels, keel too, Pine is fine.

Brink suggest willow (cuttings) for the ribs. that's The one unique part to his method. Where you live and wether willow is available, only an Arborist or a good nusery in your area could tell or help you find it. I know a guy in CA who built one and he found willow. I wouldn't know willow if I was standing on it.

If you don't go with branch cuttings, use oak or ash and cut it into ribs. Green (freshly cut) oak will bend with now steaming just like the willow. I wouldn't hesitate to tracd down and contact Brink himself.