This is one body's answer, not the sport's. You are bound
by whichever body sanctions the event you enter, and where both govern you,
you are held to the stricter of the two. The differences are set out in
the rulebook comparison.
Vintage SC is the exception in form: it uses a steering WHEEL, and aftermarket wheels must resemble OEM.
Where it stands, class by class
20 classes, grouped by the answer rather than listed one by
one, because an answer that holds for a class usually holds for every class
that borrows its rules.
Legal 20 classes
Aftermarket steering shaft, steering shaft holder, handlebar holder and steering cables are allowed. Quick-turn modifications that alter the steering ratio are allowed in most stock classes.
Aftermarket steering shaft, shaft holder, handlebar holder, steering cables: if the rule your class applies reads
differently to you, or the rulebook has changed since this was read, ask.
We answer with the section we read it from, or that we have not read it.
Ask a rules question.