Moped Army

so im not to the piaggio deal, all tomos and sachs not huge on vespa when it come to information, bu what im asking is i wanted to grab a 73cc kit off treats but i dont know how to find what pin size mine is. its a 1980 vespa grande - so if you might have information like if its either a 10 or 12mm pin, or how i could find out id appreciate it thanks