i did some searching and only found one thread that was about 2 years old and really didnt help at all.

i know its still gonna be a bit difficult, but i would think using autometer (or any aftermarket gauges for that matter) would help bypass the wiring nightmare involved. theres several on ls1tech with 4th gens running autometer gauges in their ls1 4th gens. so i would assume it would help do away with the stock 3rd gen harness all together. thoughts here?

 

I'm a little confused but if you are considering replacing the factory gauge cluster with autometer gauges, then the process will be moderately challenging.

1.) with the correct shop manual (not haynes) for the vehicle, identify which wires are for the blinkers, high beam indicator, tach signal, oil pressure signal, fuel level, water temp, and volts. Depending on the year, the speedo will be mechanical or electric.
2.) on most GM cars, the tach will be white, the oil pressure will be brown, the temp will be green, the fuel will be pink or pink/blk and the volts will be pink.
3.) if you are using electrical gauges, you simply splice into the correct wire. Mechanical gauges will use their own hookups.
4.) Now you will have to power the gauge lights, this will be done with the grey wire you identified through your manual and then connect the ground.
5.) try to use the wire at the dash and not cut them at the motor so the computer will still be getting the signals it needs.
6.) If you do nothing more than use the specified wires needed, the SES and seatbelt lights will work as normal and it will be as though it came from the factory that way.

Thankfully GM uses the same color wires for their many different platforms.

 

It's not a wiring nightmare to wire up the stock gauges to an LSx setup, about the same amount of wires that is used to wire an LTx setup, which totals about 8-10. Since you have an electric speedo, you have it covered, all of the gauges come through the bulkhead connector currently in the car so all it takes is a little time tracing out the correct wire and hooking into it, which you would end up doing with the aftermarket gauges.