Here is a New Brake Hold Down Kit with Return Springs. (will do 2 wheels Rear ONLY) As Original for your 1961 - 1966 Cadillac. These will work on 12 x 2 1/2"  Brake Shoes, Will not work on all year & model Combinations.
This is the most complete kit available. Depending on your Year & Model, you may have to reuse some of the parts that are no longer available new.