A/C Compressor Relief Valve

According to ROCKAUTO this part, Four Seasons 35753 Pressure Relief Valve More Information for FOUR SEASONS 35753, fits a 1970 Dodge Dart RV/RV2 A/C compressor. I looked on the compressor on my car and in the factory service manual and I couldn't find where it's installed. Does anyone know where it's located on the compressor and is it a good idea to replace it? I'm trying to get my A/C working.