I have an early '70s 60. I have replaced the feed throat and the buffer. The new feed throat has an additional stud on it which can be ground off to fit. I eventually got the correct feedthroat from Marlin, but it took a couple of tries and in hind-sight wasn't necessary. At least now I have a spare. The feed throat is a problem with this vintage because it was pot metal and after thousands and thousands of rounds it wears a grove and won't function properly. If you're taking the lower assembly apart, you might as well replace the springs and buffer too. Take photos of everything, be careful where the wires go, and don't loose the springs. Good luck