Brake pedal, MC, pushrod issue

Vehicle is a 73 Dart 340 Sport undergoing restoration. Got rid of the power brake booster but kept the new master cylinder I'd purchased for it. Bought an adjustable pushrod from Dr. Diff and set it to the length of the original factory rod. Bled the MC, bled the brakes. Pedal is firm and stops about an inch from the floor. When I release the pedal, it does not come all the way back up. Looking under the dash, the MC piston lacks about 3/16 inch of contacting the circlip. I can pull the pedal up until the piston contacts the circlip, but the rod will continue to move another 1/4 inch or so after that if I continue to pull on the pedal. The rod cannot be pulled from the MC from under the dash so I'm guessing it's seated correctly. Any suggestions would be appreciated.