[ford38v8]

First, since you said you're" considering", I'll try to talk you out of it: The '37-'38 Ford cable brakes are known to be the superior brakes of all Ford cars, to and including 1948. They are reliable, of course never leak fluid, and as Henry said, "The safety of steel from pedal to wheel". One small modification to Ford mechanical brakes is in order: Install floaters and they will make a believer out of you.

Now to answer your question about specific point deductions: Pre-1939 hydraulic brakes will cost a standard mandatory deduction of 20 points. Modifications made to accommodate the installation of hydraulics may cost additional points, including but not limited to holes drilled for brackets, slots in inner fender panels to pass brake lines, and the like. These additional point deductions may or may not apply for various reasons, but likely wouldn't be more than an additional 3 points for a very neat installation.

You should also know that there are many pre-1939 Fords that have won a Dearborn while having juice brakes, so it's not impossible to do. It does require an extremely experienced and knowledgeable restorer with unlimited resources to overcome the heavy point cost of the modification. Good luck, and I hope you understand that most judges are perfectly capable of finding a few discrepant items on the most perfect cars.