Joe, if it's an electric hydraboost, I am opposed to it. Buick Reatta had the Teves ABS system from Germany. If you search the AACA or the net, you will find that system caused many deaths and terrible accidents:
Accounts included folks who stood on the brake pedal with NO slowing down.
Many Teves owners stripped that system off and retrofit Camaro vacuum boosters. Others spent two grand for brand new Teves components just to find they failed early as well.
I come from an electrical background and normally I would rave about any electrical advancement. This is different and I would not have it on my car or subject my family members' lives to it.
I know Classic Car power brakes are not easy to retrofit and I believe your car needs power brakes in today's traffic. If you need to relocate the battery to the trunk to get power brakes, that is a small concession. You should do it. I retrofit Granada spindles and disk brakes on my '55 Ford Customline. I urge Classic Bird owners to do the same.
Joe, it is possible to fabricate a firewall booster bracket on an angle. That would raise the booster and move it toward the fender. Yes, the battery is in the way but after it is moved, a conventional vacuum power brake system with a dual master cylinder and proportioning valve can and should be used. - Dave