The D20 engine is the most abundant Focus engine and you can easily and inexpensively find one to replace yours if it is shot. Rebuilding it might actually cost more than just a simple swap. You can find these engines for just a couple hundred or so.
05 ZX3: 15.90 Quarter Mile Best official reaction time: .0004
New: 04 SVT : K&N panel filter, 3 performance motor mounts, Taylor wires