I have a auto gauge rev counter with shift light, can I wire it up to work as a rev limter? take a ground wire from the coil to the shift light then to ground? in other words use the light as a switch?

you probably could through a relay though...so the relay you would need to get would be a normally closed and when the shift light comes on itwould energise the relay to become open and that would cut power to your coil (which would probably cut your connection/signal to your gauage altogether so not recommended). When u get your electronic ign you would use it to cut power to your ign module, therefore acting as a rev limiter. However this would not have any influence on a miss shift ie when u go from 3rd to 4th and you miss 4th and go to second thereby causing an over rev. A series are pretty good anyway and will valve bounce and lose power indicating you need to shift up.