Hey mate, figured id help you out and shine some light on this situation.
I work for the RACV, and we are pretty clear on our terms in regards to aftermarket extra's and modifications for ALL of our policies, and unlike all of the other insurance agencies, ours is very simple.
Provided that all aftermarket extra's and modifications are legal, they are fully covered on all of our policies.
We do not list a single extra or modification on our policies, as we cover your car 'as is', and don't try to void our claims just because someone may have forgotten to tell us something that they have on their car.
Also, if your car is written off and you are insured for 'market value', we assess your vehicle, and include all non standard parts in our pay out figure, which includes anything from simply lowering your car, tinting your windows, putting in a sound system, right up to the most extensive of body or engine modifications, but only again if it meets what we classify as "registration requirements".
So if its road worthy, and legal for you to have on your car, then your covered.
Hope that clears things up