I'm no expert but I will try and help. I grabbed an old flywheel and a new disc. The hole in the flywheel where the springs sit was 5 and 3/4" diameter. The heads of the rivets was 6" in diameter. You would think they would hit, but the thickness of the disc kept the rivet heads from touching the flywheel. If your flywheel center is 5 and 3/4" you have a correct flywheel. But your disc may be wrong.

I hate the B&B style clutch. Too much pedal effort. 11" diaphragm is the way to go. I have changed to a new disc on old flywheels and found the same problem as you. Not enough adjustment to get full disengagement and still have 1" free play. I have gone so far as to remove the Z bar, and drill a new upper rod hole about an inch farther down. That changes the geometry of the linkage so that for the same pedal travel as before, you get more lower push rod travel. Pedal effort goes up a tiny bit, but with a diaphragm clutch, pedal effort goes down as the beleville spring gets over center. Another plus of diaphragm clutches. An extreme fix, but short of getting a brand new flywheel, and all new parts, it worked for me. Pic is my station wagon with 4 speed manual trans. Same issue.

Remember that the geometry of the linkage is such that inches of pedal travel results in millimeters of pressure plate movement. It does not take much flywheel or component wear to mess things up. All the factory adjustments are based on new parts so as things wear you get issues like you described.