Just as easy to fit a new seal kit before it goes on the car.

Anyway , this is what the police drivers do in the Uk before taking the high speed patrol cars out.

Get in the car and place foot on the brake pedal and press down hard and keep it pressed down hard for around a minute,it should stay in the same position and not sink down.

Keeping the foot on the pedal hard start the engine,the vacuum will pull the pedal down a bit upon where it will then go stiff as it was before the engine was started.

Keep your foot down hard for the next 3 minutes,in this time if the pedal has not moved any further down then all is ok.

Now this may work out fine when tested on the donor car but sods law dictates the seals will give up when bleeding the system on the new car it is fitted to,so it would really pay to fit new seals.