They will work just fine. Make sure the $40 price is for both the gauge and thermocouple. I'm running a Caterpillar pyro in my 3500 that I picked up new surplus for $15, working great for 6 years. Surplus Center in Nebraska, 800-488-3407 sometimes has new surplus pyros and other goodies for insanely cheap prices. Ask for a catalog, you will get nowhere on the phone. No internet sales.