The REO used all the brake lines and systems from the C60 (probably a Cab over engine model). I picked tom's brain about this about a year ago but my notes are back home.
The airpacks in those trucks are actuated by JUST air. That's the point - the cab tilts, and so they just use flexible air hoses at the hinge - otherwise, it's alot of hydraulics being pushed around (and would be a heck of a flex line). Much better to have pneumatics on the COE's.
I grabbed all the brakes off of a Hino COE truck. I was thinking of doing the air only setup, but it has no strictly hydraulic backup capability. I am thinking now of taking the air input on the deuce airpack, splitting it, and then running another air line to another air pack. That way, I'd run the stock circuit just to the front, and the rears would be powered by their own seperate circuit (the new one). In the event of catastrophic air loss, I'd still have the stock brakes running to the front (which I could totally strongfoot), and then the rear, I'd have the rear propshaft ebrake (for a one time, shoe-melting stop), you know, since the front driveshaft will be disengaged in the event of total air loss.
Yours in worst case scenario planning,
Bob