I think we established with a fair level of certainty that the bike is a 1994 Kilauea. Gil_M on this site could supply you with authentic reproductions of the decals, and in my view that would improve the look of the bike and certainly improve its value if you ever wanted to sell it. I haven't seen any reproduction decals on eBay that look authentic, so I would avoid them.
I personaly wouldn't use the Kona Custom decal and I'm surprised you've been offered it. I guess Kona are no longer interested in protecting the validity of the product, but at one time they only supplied those decals to Kona dealers and they were sold only if the buyer proved he had a US hand-built Kona to put it on. Modified by a local shop doesn't count I'm afraid!
If the Tange Prestige sticker is the blue one saying Concept, I would use it (seat tube, facing forwards, just below the top tube). Otherwise I wouldn't - standard Tange Prestige is a different and cheaper tubeset, so you're not doing the frame any favours by sticking a standard Tange decal on there.