i've been looking around at keyboard options for my SPARC system and I was surprised when I saw your project on cohost; by chance have you had any experience with the sun type-3 keyboard interface? my sun-4/110 is one of the early SPARCs before they switched to the mini-din type-4 keyboards.
i'm afraid not :( my oldest sun machines are sparcstation ipc, which is still type-4. i wonder if the type-3 is electrically similar?