Rally dash gauge voltage. 5v or 6v nominal?

Glen, I prefer using the 6v chip. It's half of 12 and applying 6V is a good way to calibrate gauges so they see "half" of their reading. That's my opinion, I'm sure some will disagree. I've made a few instrument IVRs using 5V and 6V and they seem to work about the same, so it's probably a toss up.