Ford 2003 Mustang Workshop Manual page 1100

23. Rotate the crankshaft so the number one piston is at top dead center (TDC) and the key is at
the 12 o'clock position.
24. Turn the camshaft sprocket so that the keyway is on the bottom of the camshaft.
25. Install the timing chain, the camshaft sprocket and the crankshaft sprocket as an assembly.
26. Make sure the timing marks and the keyways are aligned.
27. Install the camshaft position sensor drive gear and retaining bolt.