72 C20 rear end

[72 K20]

I have a 72 C20 , originally a 402 TH400, coil spring truck. it has a Dana rear end.

My question is concerning brakes.

What determined what size brakes were installed on these trucks ?

Was it engine ? trans ? coil or leaf spring ?

I noticed that the brake shoes are listed by spring style and are 2 different sizes ,,, why would spring style dictate brake size ?

Thank you in advance for any and all information !

Have a great day !

Tom