I’m doing brakes on the back of my 55 crown Victoria and found that there is a part missing, I don’t know what it’s called but it is the flat metal piece with a a notch on both ends that goes between the brake shoes.  It’s about 6” or so and goes just under the brake cylinder. I think it anchors the shoes.  I have extra backing plates and hardware but I don’t have this part. 

I think you're looking for an Emergency Brake Equalizer. My research indicates that the same part was used on all models from 1952-1960. Hills Automotive shows part number 2A642. It costs $19.95. 

couldnt think of what it was called  thanks  i will look up hills automotive   i may call my son he has parts that go back to the early 60s he might have something  i do have a backing plate that i thought was 50s but that equalizer is flat on one side and 90 degee on the other  might be a pickup

Glad to help!