Gene,
How do you plan on using your truck?
Your 2-1/2 ton truck should be fine with good working brakes with all new lines and hoses. I've put 30K miles on my '57 Fire Engine that weighs 14K pounds with all stock brakes. If you really want the dual pot system look at the systems used on International school buses from the 70's or 80's. The tricky part will be installing a booster as you currently have one Hydrovac. Maybe one of the fire wall mounted booster/MC's could be mounted under the floor like the original with a long pushrod from the stock pedal (move it way back on the frame so the angle is not as steep).
I can't help with the disc brake idea...
Mike B
