Well Eckhard you certainly led me down the rabbit hole. I was about to leave for my Valley Center workshop and now I'm about ready to buy a $50 CANBUS 2.0a OBD-II scanner (waiting for vendor to verify capability). I've also asked the same question of several HUD vendors although I'm not interested in a HUD. I guess I'll work in my driveway this afternoon (I'm taking bodywork apart for my CANBUS project).
But in the meantime I followed the ELM327 thread at the bottom of
https://en.wikipedia.org/wiki/OBD-II_PIDs
Since my project involves an Arduino Duo I wondered if someone built their own HUD using the ELM327 and an MCP. Nope. Not someone. A whole bunch of people! And the software libraries are on GitHub. Took a look and they're kinda nice. So if someone wants to build their own HUD (or auxiliary console display) of OBD-II data the hard part has already been done. You just need to wrap some weathertight hardware around the circuit boards and connect to the DLC1 port.
Back to the HUD -- here's my offer to a pre-2018 Spyder owner: choose (but don't buy) one on Amazon and tell me your choice. I'll verify CANBUS 2.0a compatibility with the vendor. Then you send me pictures of your DLC1 connector that clearly show wire colors and pinouts. If it's a 6-pin Deutsch DT with 5 pins populated (WH/BG, WH/BK, OR/RD, RD/YE, BK) then I'll buy the HUD, fabricate the Spyder-to-HUD cable (which will plug into the DLC1 connector for CANBUS signals, 12V power and ground), verify its operation and send it to you. If it works on your Spyder you pay me materials and shipping.
Now I'm leaving the rabbit hole for the driveway.

hyea: