That's the very definition of an OBD1.5. It's a bastardization between the older computer, and newer ALDL connector, thus why you have to find an OBD1.5 specific scanner in order to retrieve any codes.
That being said, what FFDP listed is all you need to make a HUD work. In fact, the HUD units themselves for the '97 - '03 are identical to the '94 - '96. Just a couple wires that need to be switched around on the harness, and you could make a newer one work right now.