the easiest way is to get a 1.6 efi mk5, then you can literally stick a fiesta rst lump in, sort out the exhaust and intercooler (although I'd stick an escort t3 turbo on it straight off - helps with airbox and exhaust issues).

You can plug the ecu straight in to the loom, the only thing missing is the amal valve wiring, which is very easy.

You will need to get the right type of ecu for the mk5 loom you have. OFAC or OFAB. Mine was OFAC.

If you go the escort rst route, you will have to fanny around alot more!!