273 torque converter
Your 5.9 Magnum needs the harmonic balancer and flex plate it has on it. If your converter is a 68 and up, the nose of the converter and the crank register may match up, but be sure and measure them both as mentioned above. You will need to oval one hole in the 5.9 Magnum flex plate for your existing converter to bolt up. Your existing converter should have no weights welded to the face of it. I'm sure you will change the front seal in the transmission during the process. Have fun with the swap. It should wake your car up a bunch!