Hewitt pyramid install?

Pretty sure the wires are specific resistance.
I;ve installed 4 or 5 pyros and I've always just used the supplied wire that it comes with. There's normally two different types of thermocouplers as well. One type has two wires coming out a yellow and a red, the other has a yellow, red and then an uninsulated ground wire. You also want to make sure the thermocoupler is the right size pipe thread for the bung in your exhaust. You don't want to have to use a bushing/reducer as it will usually make the thermocoupler sit too high in the exhaust and you won't get an accurate reading. Make sure the thermocouler you get is the long one and not the short stubby one meant for manifolds and cars.