I would recommend replacing the rubber lines going to the brake cylinders in the front (1 each side), and then replace the one rear brake hose that connects to distribution block on the rear end. These rubber lines break down over the years and will collapse when applying pressure to the system. I have also had the rubber expand so much as to pinch the inside of the line so much you couldn't fit a toothpick in there.
Replacing the rubber lines isn't hard to do, toughest part is having a good grip on the metal lines to break each one loose, without damaging the metal line or nut.
Good job, keep up the good work!