the pushrod needs to be inspected that applies the force to the master cyl piston. the distance it protrudes from the booster needs to be compared to a good working vehicle.
the pedal and the brackets braces etc that carry the pedals need to be inspected for a cause if pushrod is too long.
extra parts being found at the area where the pushrod contacts the piston, or something at the snap ring in the m/c bore between the piston and the snap ring.
i have seen cars where there were also 2 places to attach the booster rod at the pedal. look in all the above areas for something thats making it protrude or not allowing it to return fully.
or/ the cars bent. someone had to slam the brakes on with both feet and stood on it and they were big and strong. now the distortion of the parts is not allowing full return???
or you could stay close to home till you save up for some more parts