If the master cylinder is close to 30 years old, obviously replace it. Braking will improve exponentially. Before you do that though check all the metal brake line unions to make sure they are screwed in tight, I've seen some cars where they vibrate loose. Check the lines to the MC and to the calipers. If they are all tight then it is all due to MC failing.

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1985 CA 300D Turbo , 213K mi