im looking to make this simple on myself so i am just replacing the factory gauges and then just adding a tach. because of that is the stock spedo a mechanical or a electrical. and if i buy the same as the stock will that make for a simpler install. and on the fule level gauges it says "0 Ohms empty / 90 Ohms full. For most GM vehicles from 1965 to present." i assume this is what i need but just wanted to get one of yall to verify it for me.