Bullmastiff Breeder Wanted

I am looking for 2- 4 large dogs. My experiences are with German sheperds, Doberman Pinschers and Rottweilers.I`d like them to have as part of the family but guarding my land which is partly used as a fishfarm.I am also open for an offer in American Pitbullsor other dogs in a comparing size. I prefer race dogs but I wouldn`t bother if they were a result of a mix. But the size is important. Height above 50 cm and weight above 45 kg. thank you for an quick answer. Greetings Jurgen