You will need to verify the condition of the master and the hydro-vac before doing anything else with the brakes. That will make or break your chances to drive it home.
Ensure the master isn't leaking any fluid out the rear seals and into the boot around the rod that connects to the brake pedal. Its not always obvious, so assuming you have brake pressure, pump those suckers repeatedly and feel around that boot and gently squeeze it. Sometimes its obvious as there is fluid on the inner firewall. Sometimes it not but squeezing that boot will result in both feel and sound of fluid in the boot.
Assuming all is well, run the truck and while stationary spend a couple minutes pumping the brakes. Then shut her down and pull the vac lines of the hydro-vac. If there is any fluid in the vac lines then the hydro-vac is shot and you can expect replacement to be weeks away.
Since your at it, inspect all vac lines as well. The factory steel lines if not yet fully corroded away, will be shortly and will cause loss of vacuum for the engine. That's an easy fix with modern hose though.
And a word of warning, that new Rochester carb (depending on where you bought it from) may not actually work. The brand new one I purchased would not idle down and the accelerator pump was messed up and refused to come off throttle. The original, slightly leaky one I had is the one still on the truck. The new one is now chopped for parts that cant be had in rebuild kits. Keep it in mind and don't let go of that old original Rochester.
