This is the plug that is used on the brass T-Fitting for the later mid year 1964 and 1965. This is for the larger port in the T-Fitting that is for the 3/16" line. This is the 3/8" plug. There is both a smaller and larger port on the T-fitting for 1964, one is a 1/8" line and the other is a 3/16" line. Measure what you have before you order. If uncertain ask.