If you mean the sender for the temp gauge try a TS 6464 from NAPA or a TS-4 from others. Here is a report on the senders DrewLA worked up. The same sender should be fine on all 51-56 with exception of a few 51 or 52s that came out of the factory with a gauge issue and had to have a calibration resistor or special sender installed.https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=165532#forumpost165532
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