I agree with Tom. The pump is the way to go. you can also go with a smaller booster if your not looking for that stock look. i dont think a 9/16 hose will add much difference.
You can try that but it will still be the same.
I installed a vacuum pump on my 70 SS and have never looked back. No more brake issues.
Or you can get a hydroboost system. I went pump. Cheaper and kept the stock look of the engine compartment. I installed the pump under the front fender behind the washer bottle. Out of sight and so are the lines.