Tyre speed rating

Have been looking at what tyres I can put on my Terracan they have a speed rating of 106t but after looking at vic roads web site and coopers tyres I have found the following

From vic roads

for vehicles with a GVM of 4.5 tonne or less, with four or more wheels, the lesser of:

140km/h for a passenger car with special features for off-road use such as 4WD;
180km/h for any other passenger car;
120km/h for any other motor vehicle not described above;
the vehicle's top speed.


And coopers tyres web site

The Speed Symbol means the tyres are speed rated on an indoor test wheel. In Australia it is legal for any 4Wdrive to be fitted with a N rated tyre which is 140kmph, this may be lower than your original tyre. Speed ratings are completed under extreme conditions with excessive weights and at excessive speeds for extended periods of time

So what is the go will my insurance pay up if I put a 255 16 111s on my terracan can anyone explain what the go is

Thanks Tim