Been reading through the whole thread. Great information. Forgive me if I miss somethings, but it is such a long thread it might not hurt to revisit, at least that is the excuse I am trying to use. :-)
My question may be best broken up into two areas, one cosmetic the other interfacing. For now to narrow the context I am going to ask from installing a DIC, but can be expended to HUD and maybe something custom.

Interfacing:
Sounds like I maybe boxed into a corner, since I have a 97 GP GT. In my shelter life all I have ever seen is analog DIC on my 97, 02 SE, 02 GP. Once I moved into the 06 (two of them), 07 GXP then I saw a digital. After doing some googling I did see where someone was selling an earlier model digital. Looking at some of the names of the wires there seems a mixture of signals. Some are "a wire (bit on/off)" and "bus (communicated serial?)" I know you stress 97's only 97's. Is that because of connectors? It was mentioned because of "tire pressure" notification. What's/How is the sensor? What about using a latter model digital (cosmetic issue discussed in next section)?

Cosmetic:
Adding a round peg into a somewhat square hole? Of course the cosmetic is mute point if interfacing can not be worked out.