Ford 2003 Mustang Workshop Manual page 1318

CAUTION: Camshaft keyways must maintain a 90 degree clocked position relative
to the valve cover rail.
CAUTION: To prevent piston crown and valve damage the crankshaft keyway must
be clocked at 270° (45° BTDC) before the installation of the cylinder head assembly.
NOTE: Crankshaft must be rotated clockwise only.
Align the keyways as shown.
32. NOTE: Position the RH and the LH cylinder heads over the dowels on the cylinder head
gaskets.
NOTE: The LH is shown the RH is similar.
Tighten the bolts in six stages in the sequence shown.
Stage 1: Tighten to 40 Nm (30 lb-ft).
Stage 2: Tighten an additional 90 degrees.
Stage 3: Loosen the bolts a minimum of one full turn.
Stage 4: Tighten to 40 Nm (30 lb-ft).
Stage 5: Tighten an additional 90 degrees.
Stage 6: Tighten an additional 90 degrees.