Power Brake Pedal Linkage Spring

I am missing the power brake pedal linkage spring on my 68 charger. Does anyone know if this part is necessary or what the purpose of the spring is? I have driven the car around a good bit without it but am doing a 4-spd conversion and in looking at diagrams see the spring that I have been missing the entire time I have had the car.

Are you sure that's not a clutch pedal spring you are seeing? I don't remember a spring on the brake pedal.

I am sure. Here is a picture of a power brake pivot assembly.

Ok, I get it.