Ford 2003 Mustang Workshop Manual page 1348

17. NOTE: The LH timing chain tensioner arm has a bump near the dowel hole for identification.
Position the LH timing chain tensioner arm on the dowel pin and install the LH timing chain
tensioner.
18. Remove the retaining clip from the LH timing chain tensioner.
19. Position the RH (outer) timing chain on the crankshaft sprocket, aligning the copper (marked)
link with the timing mark on the sprocket.
20. Install the RH timing chain on the camshaft sprocket, aligning the copper (marked) link with the
timing marks on the sprocket.