The beginners guide gives all that is required. Key are 2 spring on carbs/tbs, clearly marked ignition, 1l catch tank, tow points marked on roll bar and being polite to the scrutineers.
Even after many years of competing with your car passing scrutineering every time you will still come across a scrutineer with his own pet compliance topic.
Roadgoing cars have to have front and back number plates, never been pulled up on size but have to be there. I was pulled up with tyres that slightly protruded from the front cycle wings. These types of problem normally come with a comment and advice but don't tend to stop you competing. Also the camaraderie of the WSCC will have any issues sorted quickly in the paddock and successfully back through scrutineering.
It can be a bit daunting the first time through scutineering and I would highly recommend getting one of the local WSCC area speed series guys (Garry or Del) to take a look at your car, their experience will soon identify any potential problems.