In case you have to search for the assemblies anymore, here are the part numbers for the two types used in 1957: 1st type -
1513311 & 2nd type -
1513541. The first type had some owner complaints about showing hot when everything was still normal. The second type was used later which has a higher scale that prevents false alarms. See attached Service Bulletin from 1957. At this point in time, either type should be usable if you can come across one of them.
There are also some cautions to review in the Shop Manual on pg. 10-72 and -73 (available on this site) about training the capillary tubing as it leaves the engine.