These are the proper voltage reducers you want for your gauges. They go right on the back of each gauge and convert 12v to 6v. You can use your stock 6v senders and your gauges will never know the difference. $18 ea. Call 800-732-6029

Tech Tip: Use these reducers and your original flathead senders in later model engines and you can use your factory gauges with any type engine you run.