69 Coupe Low Brake Pedal

I had an issue like this. Converted to disc and dual bowl Mid 70s ? master cyl. Ended up being the pushrod was too long keeping the piston in the master cyl pushed too far forward so I wouldn’t get the proper amount of brake fluid pushed into the system.
I ended up cutting my rod shorter and making it adjustable. You can check it by disconnecting the rod at your peddle and letting the master cyl position the piston then hold your peddle up against the peddle stop and compare where the rod sits in comparison to the connection on the peddle. You shouldn’t have to push the rod in to connect it to the peddle or maybe just slightly. This will position the piston in the completely retracted position where it should be and give you full travel of the piston.

Yeah the rods can be the same length but the pistons are different, just a thought.
Yeah your rear shoes could need adjusted too. They should be adjusted so they drag slightly when you rotate the drum by hand. Just make sure your parking brake is completely released before adjusting.