This temperature gauge fitting is correct for 1930-1940 Chevrolet cars & trucks. It can also be used when adapting a 1955-1962 6-cylinder engine into a 1954 & earlier car or truck. This fitting will reduce the size of the hole in the later cylinder head to be used with earlier temperature gauge fittings. It is machined with the proper internal shoulder (seat) for the temperature sender. Dimensions: OD of threads .835", ID of threads .575", Hole size for temperature bulb is 1/2", with tapered shoulder. Replaces GM# 597630, 358147