I don't think having the original top is a big deal from the standpoint of materials. I don't think there's anything about it that you couldn't get today. It's just a nice thing to have because it shows an aspect of the car that was preserved. In the case of my current SL, it was probably a very nice top when they swapped out the window, but today it's just okay. It has the typical fraying in the corners, but no real damage and it has that nice snug factory fit. You can tell it's factory because it has the metal bars embedded above and below the rear window.
I guess what I'm saying is not to stress too much about swapping out the top for a new one. I don't think the originals are appreciably better than a good modern top using the original materials.
Douglas Kim
New York, NY
280 SL #016220