65 driveshaft possible upgrade

65 Plymouth valiant, 340, 904 automatic floor shifter. It has the “ball and trunnion” front joint on the driveshaft. Has anyone had any success in upgrading this type of driveshaft? I would like to keep this transmission as long as I can upgrade the driveshaft. I don’t plan on having big horsepower in this car. Right now the engine is stock with a cam upgrade… “purple shaft” I was told. No idea what that is.