27.0mm and 31.8 are the correct sizes as previously posted.
Steel frames are also 27.0mm too. The only 90s Kona frame I know of which has a 27.2mm post is the 1997 Kula (no idea why though, but assume different tubing is why).
Funny you should say that because my 97 Kilauea came with a 27.0, but I found it needed a hell of a lot of clamping and other owners seemed to find the same, so I fitted a 27.2 Syncros, which is a perfect fit. However neither of my 27.2 posts will fit in my 97 Lava Dome - and the 27.0 in-line Race Light that is in it came off some guy's Hei Hei!
I think the detailed frame specs that I used to have (but no more - hence I'm jealous!) show the Kilauea as having significantly thinner tubes than the lower-spec frames. So I kind of speculate that if the external dimension is the same and the butted end of the tube is even 0.1 thinner, then the post needs to be 0.2 bigger, but maybe that's too simplistic?