DDK - Die Deutschen Klassiker

The exhaust system on my 1967 912 has a cylindrical box which extends the full width of the car; I will need a new box soon and the examples I have seen in parts catalogues/on Ebay seem to have a much smaller box, extending only half the width of the car (on the nearside). Is my system normal - or does it not matter?

Obviously you need to get the right silencer for your system, sounds like you have a stock exhaust (only a pic will tell the full story) if so Dansk make a good replacement.