Everyone is not doing it and with good reason. Its a '70's car not a current model which is designed and styled to have bigger wheels. All the race Zeds I know have 15" wheels, except one which has 16" to accomodate big brakes, wide tyres and 500whp.
I have yet to see a S30 with 17" wheels that looks good, particularly because most of them don't have wide rims.
Oh dear, this is way off topic, stop right now