If I read it correctly you want to refit the wheel cylinders into the backplate? As long as the wheel cylinders are now free squash the fingers with water pump pliers or a G clamp and then refit to the backplate. You can test if the cylinders are working by having an assistant press the brake pedal which will then open the fingers. To close them the assistant removes his/her foot from brake pedal and you squash the fingers back together with the water pump pliers.