I just had a very reputable repair shop do a complete drum brake overhaul on my 1956 Crown Victoria. Every component was replaced: brake line, brake hoses, new drums, new shoes, new 7 inch dual diaphragm booster, new dual master cylinder and all new drum brake hardware. Car stops okay however there still is what I consider an unsafe condition that they have tried and tried to correct to no avail.
The gap between the brake pedal and the accelerator is very narrow (maybe 0.5 inch) and when the brake pedal is depressed the first time, it goes approximately 1 inch past the accelerator pedal. After depressing the brake pedal the first time then pumping it again a second time, then the brake pedal will not pass the accelerator. When I was backing out of the garage, I attempted to stop the car. My foot pressed on the brake and when the brake pedal passed the accelerator, my foot also caught the accelerator and the car sped up instead of stopping. It scared the living hell out of me.
I realized what had happened and now know to be more careful when braking. I cannot let anyone else drive the car with this condition. The shop told me they tried every adjustment possible to correct the low brake issue. They are stumped.
Two short term things I am going to try is to change out the longer power brake pedal with the shorter non-power brake pedal and possibly putting some kind of spacer (block of wood?) under the brake pedal to prevent the pedal of going past the accelerator.

Does anyone have any ideas why the brake system is having this issue? Should I remove the brake booster completely and just have regular brakes and see if this is the issue?

Thanks,
Danny