I didn't say they came with power brakes for no reason. I said just adding a power booster doesn't improve your stopping power. And it doesn't. It does make the pedal easier to push, and that might be more necessary on larger vehicles because your need more braking force. That can lead to higher pedal efforts, which people don't like. But just adding a booster does not increase stopping power.
Now, if you
design a brake system that has more braking force and higher pedal effort based around using a booster to make the pedal easier to push, you can have more braking force than would be easy to use with manual brakes. But that's not what's happening here.
Thanks for the clarification. You're not wrong, adding the power booster would reduce the effort it takes to push the pedal and it sounds like that's what you want to take care of. To install the power booster you'd need the power booster and the mount/linkage that's used on the A-body platform to raise the booster and m/c on the firewall. You'd also likely want a new m/c, as the manual brake cars and power brake cars ran different cylinder bores.
Here's a picture of the A-body power booster set up. Power booster, angle bracket, and a pivot linkage for the push rod
View attachment 1715077673
But, that's not your only way to reduce braking effort. You can change the size of the m/c bore, which also has an effect on pedal pressure. Stock '73 A-bodies with manual disks have a 1-1/32" m/c, and it gives a pretty high and hard pedal. I run all of my cars with manual disks with a 15/16" m/c. I even converted my Challenger from power brakes to manual. The stock power brakes just don't give you a whole lot of brake feel. The manual 15/16" master cylinder works well for that, the brake effort isn't bad at all in my opinion, and the longer pedal stroke allows for better brake modulation.
