I've built 50's and 60's trucks with both power and manual brakes. If you are upgrading to front discs, I've noted that adding a power booster, even with a properly designed system (no ABS) can become very twitchy under heavy braking.
My current 54-3100 with manual corvette master, front discs, adjustable proportioning valve is much more predictable...has better feedback and is less likely to lock up under heavy braking.
I found the power assists were so sensative that under heavy braking, your own body weight moving forward, can compound the pressure on the brake pedal. If you choose to run 4 wheel drums I might be more inclined to opt for power assist.
However, I would drill out the 1/8 NPT fitting on the intake to 3/8 NPT to obtain enough volume of vacuum.
On the 9" booster I would dispose of the stock proportioning valve setup and go with an adjustable valve...fewer plumbing and bleeding problems. Being able to control rear bias will be to your advantage.
There is a lot of good brake info at the following sites:
http://www.ecihotrodbrakes.com http://www.mpbrakes.com http://classicperform.com Hope this helps.
Dave
