New master cylinder, brake pedal on floor next morning??

They came that way for years with the small tab and worked. You can not pull up on the pedal or you will pull the piston out. The cast M/C are fine to use. After all they worked on many cars for many years before the aluminum ones were made.
Dumb *** tow truck drivers will use a seat belt to tie the steering wheel in a fixed position so they can keep the front wheels straight. They would tie the belt from the brake pedal to the steering wheel and tighten it up and you guessed it, pull the piston right out of the master cylinder on manual brake cars.