Question about installing master cylinder on 68 dart

The rubber "keeper" fits around the pushrod to keep it from coming out of the master cylinder. Your old pushrod should have one.

The pushrod can be a pain to get out. The last one I did, I loosened the master cylinder at the firewall and put a spacer in between the firewall and the master cylinder. Then I yanked the brake pedal towards the seat to dislodge the keeper.