if you're going to keep the OEM rear, then you'll really need to get the rear valance colour coded too IMO
guessing ebay by putting in mk4 rear valance?
the rear valance is the same on all MK4s apart from the anniversary, V6 and R32
the only issue you'll have is that the standard valance wont sit as low as the lines of the skirts, but it's not that much of a difference to cause an issue.