you align the TDC mark on the harmonic balancer like in the picture ( as you stand on the driver's side of the car looking at it, ONLY SPIN THE MOTOR COUNTER-CLOCKWISE )
the TDC marks should agree at the top and bottom of the motor, or your mechanical timing is off.
ok, here we go!!
first things first, you will NEVER be able to "see" the cam gear on the top end without removing the valve cover first ( spark plug wires off, leave spark plugs in, ENGINE COLD )
then you will be able to see the actual mechanical timing. I think the belt is confusing you, in that it's not the belt's alignment you worry about as much as the alignment of the top cam gear's TDC marks to the top of the block in comparison to the alignment of the harmonic balancer's TDC marks alignment to the timing cover's TDC marks.
( no head replacement required yet, might want to check valve lash clearances while the valve cover is open, though )