The kits offer a safe way to install Early Ford hydraulics without butchering anything. They are not going improve the braking any more than some of the old sketchy methods of hacking up crossmembers to install the master cylinder.
I used to read about how bad early Ford hydraulic brakes were. Mostly from somebody trying to sell you disc brakes. Then I went for a ride in Bernie Couch's '32 roadster. He had owned it since around 1938. I'm pretty sure he owned that '32 roadster longer than anyone else on the planet had owned a '32 roadster. He was a neat guy. His 1946 dry lakes, Dago dropped axle from his '32 roadster is now under my roadster project.
Years ago, when I was getting interested in this stuff Bernie and I were driving down the road in his '32 roadster, about 40 mph, I asked him how well do these early Ford hydraulics brakes work? He didn't say a word just kept driving and then he locked up the brakes and sent flying, hard into the dash and windshield, it hurt. As he was laughing at me, he said, "what do you think." I was satisfied with them. My uncle had a '35 pickup with hydraulics and I was happy with its braking. You can put Lincolns on them with self-energizing shoes which will also improve them. That is an expensive conversion.
On My 1929 Roadster, I can lockup the tires without much pedal effort, with the mechanical brakes. The brakes only need to be as good as the tire to road contact patch. The latest and greatest brakes won't matter much if the extra applied force makes a skinny tire skid easily. It just makes the pedal effort easier.
I have my dad's '32 roadster he bought maybe 20-years ago. Neither he nor I have ever done a thing with it. I drove it home to his house the day he bought it, over 100-miles, on a 100-degree day, in a freeway traffic jam, moving 10 mph or not moving at all. I was so worried it would overheat but it never got hot. What turned out to be scary was its brakes. It has pedal pressure but not alot happens when you apply it. You need to plan way ahead for stops with that car. Had I never driven something with Early Ford hydraulics I 'd still be saying bad things about what a death trap they are. Ther would not have a straight early Ford grille left if they all stopped like that one.
My dad never drove the car more than a few times around the block. Since he did not drive it. I never pulled the brakes a part to fix them. I was working on trucks all night, raising kids during the day, building a house...
I never got around to doing thing with the car. and I have of other Ford projects ahead of it. On dad's roadster, It's not the fault of the Ford brake's, it's a maintenance issue. It's up on a hoist in my garage, not to work on, just to get it the air and out of my way so I can park another car under it. I walked by it the other day and noticed brake fluid dripping off both rear backing plates. It hasn't been driven in probably 15-years. My 5-year-old grandson want me to get it going.
Bernie taught me that when everything is as it should be that early hydraulics will stop good, at least they will stop something as lite as a '32 roadster.