Are you wanting to do a vacuum brake conversion or hydroboost conversion?
It's best to do a search on which one you would like to do, or to find the difference.
I did the vacuum brake conversion on my car using a dual diaphragm booster and master cylinder from an '86 Monte SS as well as the brake pedal and push rod from the inside.
Make sure you bench bleed the master cylinder before you install it on your car to get all the air out of the master cylinder for nice solid brakes.