There are all sorts of rules in those publications and it is very confusing. Pay particular attention to the "81" series in the back part. Rules like 81.01, 81.02, etc. Those directly apply to Bonneville bikes.
One thing that makes building an FIM bike a challenge is that they want pictures of the bike and detailed shots of various parts when you submit the entry. This means the scooter needs to be put together before the last minute. Another challenge is the need to have a thorough medical exam and pass the dang thing. This can include a stress test and electroechocardiogram for us older folks.
Download the entry forms as soon as they are available and read them completely so you will know about all of the hoops you need to leap through. It takes some planning.