You can determine the true spacing of the contours by calculation or by measuring distance AB in the cross-section. Given the fault shown and slickensides with the observed pitch, find their trend and plunge. Construct structure contours for the plane. Find the true spacing by cross-section or trigonometry and construct a second set of contours with true spacing. On the true set of contours, construct the pitching line as it appears on the dipping plane.
Project distances along the contours back to the map view.
On the map view, construct the map trace of the line. Find its trend and find the plunge by trigonometry or drawing a cross-section. We know the pitch and the dip. What we want to find is the trend and plunge. It will be plus or minus depending on which way the pitch is measured relative to the strike.