[kaisen]

Just looked up my Ford parts prices (the 2005 Focus ZX4 ST hadthe exact same motor)

$30 Lower overhaul gasket set
$60 Upper overhaul gasket set
$44 Head gasket
$48 Head bolt kit
$46 Timing chain
$48 Timing chain tensioner
$18 Tensioner guide
$18 Chain guide
$53 Oil pump (shouldn't need it)

A set of four pistons with wristpins and rings should run about $225
Your rod and main bearings should run about $125

You'll likely need one new rod, maybe two....figure $50 each, new from Ford or Mazda

You'll have $700 in machining and labor to disassemble from longblock, mic everything, clean everything, pressure test head, bore/hone block, grind/polish crank, hone rods, fit wristpins, assemble shortblock, fit head, and reassemble everything else.

Soooooo...... it's possible to rebuild YOUR engine for about the same as buying a relatively unknown used motor

That's the route I'd take