Your truck is an aftermarket conversion, Ford never built a factory F250 dually, odds are your truck is a centurion or something along those lines.

My rear brake setup mimics a 70's Ford front, short flex hoses from the calipers to the axle tubes, I think I ended up with Dodge parts... LOL
As for a parking brake, the big lugs on my 44 boggers against the front leafs work pretty well. My truck is pretty much non street use, and I have a spare mechanical mico lock from work, so thats what it's going to get, it's pretty much a mechanical operated line lock.