My '55 Thunderbird has lousy brakes.  I've rebuilt or replaced everything from the master cylinder to the brake pads.  I have a good pedal, but the thing just won't stop like I want it to.   I know I can convert the car to disks, but I don't want to butcher it and I definitely want to keep the stock wheels. I'm thinking about installing a power brake booster kit.  Does anyone know what I need?  Will this make things any better?

Phil, I put front disk brakes on my 55Tbird over 15 years ago. I used a kit from Master Power Brakes. Sometime after I bought my kit I contacted MPB with a question but they had gone through a bankruptcy and the new management did not have any info about me or the kit I had bought. This kit was NON POWERED.
Anyway, I still have the stock 15 inch wheels and use a dual master cylinder with a brake proportioning valve and NO booster. The brakes are GOOD but do need a lot of foot force to stop. so if your used to a modern  cars brakes it seem wrong. Before I switched to disks I did have the power brake booster and I felt that the brakes were too twitchy ( over sensitive ) so I ended up pulling the booster off and the drum brakes were OK for 1 or 2 stops in heavy traffic then would fade away. That's why the disks.
It was a GOOD MOVE. Pete

I installed Kelvar linings when I installed the stock power brake unit on my '57
Bird many years back. Not as good as power disk but much better than what I had before. Still working pretty well. Thinking about power disk but haven't convinced myself yet.

I called T-Bird.com to inquire about their power brake upgrade kit.  They told me their kit was better than stock drums, but not the best solution.  I upgraded a 1965 Mustang to front disks before using a dual master cylinder and Granada calipers.  It stopped much better, but it did change a lot of the hardware and the wheels needed to be changed as well.  I'm not looking for modern car performance, just safety.  I may look into an alternative to the stock brake shoes.  I believe I should be able to lock up the wheels on hard braking and I can't do that as it is.

I changed my 56 using Granada Spindles and Brakes. I believe the 15 Inch Rims are the same as used on your Bird. The Hub of the Granada Rotors had to be turned down a little  bit in Diameter to fit into the center opening on the Stock Rims. Other than that there was no problem using Stock Steel Rims.