Hy IHBoilermaker, welcome, if you intend to keep the truck then I would recommend a complete rebuild of the brake system. You already have a leak, so your braking system obviously needs repairs. I would repair or replace everything, master cylinder, wheel cylinders, hydravac, flexible lines and hard lines, and of course turning the drums (if they are not already oversize), and new shoes and linings. Don't forget new return springs and shoe hardware, not a cheap job, but better that you and everyone on the road around you are safe, hope that helps.