Assuming you are inquiring about "how/where" to place the sensor bulb/sending unit...it should be placed somewhere in the water jacket where it will have coolant flow across it. My memory of most 289s is that there were some threaded plugs in the intake and/or block that would allow an additional access point. Do not "T" the additional sensor with your existing sensor bc neither will read correctly---the "T" would put them out of direct coolant flow.