Per:
My experience is with car shows in the USA. Many shows are for any marque so you can have a Pagoda next to a Ford Mustang. The Mercedes category might be "Best Foreign Car".
In these shows, the judges don't know the details of every brand so they look for cleanliness, workmanship, completeness rather than perfect originality. The items on your list probably won't matter. It's about the same in a Mercedes only show since the judges don't know every Mercedes model.
In a national Mercedes show or a show for SL's or Pagodas only, the judges probably have experience with specific models. Here your list items can affect the result.
In my experience, there is no deduction for an item that was available from a dealer at the time the car was first delivered...so there would be no deduction for a Nardi wheel...also safety items like seat belts for the third rear seat are not deducted.
The usual concours guide is "dealer delivered condition"...changes to paint color, electronic ignition, axle ratio, interior color or material can all lead to deductions. (Electronic ignition would usually be a much smaller deduction than a body paint color change.)In a serious concours judging even hose clamps are examined.
Deductions can get a little complicated. In the rules of the Mercedes Benz Club of America (MBCA), a paint color change is a 5 point deduction but only 3 points if the new color was available at delivery time; also the number of points deducted varies for 'Concours' or 'Street' category.
In the West Point 2004 event in New York on 23 May 2004, it will be a "Friendly Judging" intended to help the Pagoda owners learn more about the cars condition rather look for absolute perfection. The judge comments will be general, and the judge rating sheets will be given to the owners to keep for guidance.
Take a look the rules of the MBCA for an example at
http://sl113.org/forums/index.php?topic=398,rulesRichard M
P.S. My car, sometimes called the 'Brown Beauty' or more accurately the 'Brown Jalopy', is very original but it's not in like-new condition so even with originality, my trophy shelf is nearly empty.
'71 280 SL, Tobacco Brown, Cognac interior, Tan top, Jump Seat, 80K orig miles, NYC. Can be seen at
www.panix.com/~rmadison/mercedes.shtml