my experience converting to power brakes and power steering so far (and a question)

[sircrunch]

My 1975 GMC Sierra came from the factory with manual steering and manual brakes. I asked on here if there was anywhere that had a kit for this. The consensus was that its easiest to find a donor truck to get all the parts from. I put a wanted ad on craigslist and a couple weeks later I had all the parts I needed for both brakes and steering conversion!

Parts I got from the salvage truck:

Booster and master cylinder
vacuum line that runs to the back of the carb
the rod that connects from the top of the pedal to the booster
power steering pump and brackets
power steering box
crank pulley w/ 2 grooves

New/Reman parts I bought from the store:

master cylinder
trans fluid for the ps pump
power steering hoses
brake fluid
power steering belt


So I didn't wanna mess with a used master cylinder so I just got a new one. I gambled and used the old booster and I think that has backfired on me. I was a little bit weary of using it anyway because it had been sitting out in the weather for about 3 months without the vacuum hose in it. Could have got water down in that little hole.... but I figured it was worth a try. When I started my truck up for the first time since installing all these parts the power steering works GREAT but the brakes are another story. I bench bled the reman master cyl and bled the brakes at all 4 corners. When I was pulling out of the driveway to test them I could tell that the brakes were weak but I could feel the "power" brakes were working. But it didn't last long. After a few times stopping I could feel all of a sudden the brakes were harder to push again, just like before, with manual brakes. And now when I push the brakes, the engine revs a little. I think the booster may be bad, what do you think? If so, do I buy a JB3 or JB5 booster?