My findings to far - 1st column is my new values - 2nd is Max speed at optimal altitude.
Swordfish 202KmH Max speed 224km/h
source
Sunderland 294KmH Max Speed 334Km/h
source
Hurri 368KmH Max Speed 550 Kph at 6705 m
source
Catalina 276KmH Max Speed 288 Kph
source