Here's another wild thought from inside my head..... I don't like the looks of any aftermarket speedos that I've seen and it's alot of work to get any of them to go inside my stock Corvette dash. However, I would like some indication of how fast I'm going. How about using the signal from the VSS (or the SPEED pin from the PCM) and creating a simple circuit that has an LED readout. It can't be that hard.

Is the signal a pulse that varies in frequency with speed or does it change voltage? Has anyone thought of doing this before, or even done it? I'm only a mechanical engineer, but I think we did something similar to this in an Electronics and Instrumenation class in college.

 

The VSS will give you a varying freuqency that changes vs. speed. I would probably just use a uC if that's what I wanted to do (Atmel AVR), but there is more than likely an analog circuit design out there that can do it (depending on if you mean just a LED bar graph or a (multiple) 8-segment LED display). I still think it would look alot nicer to go with an aftermarket solution though . If you can't get the dash to your liking you can always pick up a HUD unit from DEFI and just project it somewhere (you could put a proper finish on your dash and actually reflect it there - might look kind of cool.