I know
this picture is for F-series, but all the older ford trucks I have worked on have had the same basic parking brake setup.
Generally, from the pedal assembly, a cable runs back along the driver side frame to a point near the rear of the cab. Then, it splits into 2 cables - one for each side. There will probably be some brackets and springs there to hold it up off the ground. The 2 cables clip into the backing plates for the brakes on each side and then attach to the linkage that actually moves the brake shoes when you push or release the Parking brake pedal.
You could try a junk yard and see if there are any good parts there. That way you can take pictures and see how it is all connected. Otherwise, I would think you should find most of the parts on RockAuto. You will need to know your wheelbase because the cables are different lengths depending on the wheelbase of the truck.
Oh, yeah. when messing with the adjusters, you need to bear in mind that one is left side and one is right side. The adjusting threads are opposite each other and it won't work if you mix them up.