Whats your mk4 currently running?
If you have an efi management its a doddle really.
Mine was a 1.4 cvh carb.
Im now running a zetec turbo.


Click on my sig for more pics if you want.
You will need a modified rear engine mount.
EFI managent or carbs if you wish, twin 40's maybe?
Either a Fiesta RS turbo EFI inlet or the later EFI inlet as found on the mk6 escorts.
Fiesta turbo inlet needs an adapter plate to mate to the zetec head, the later inlet bolts straight on but not sure what injectors you need to run on it really.
Either use the zetec exhaust manifold and have a matching down pipe altered to fit your car or you can drill and tap the head as I did and bolt the cvh manifold on.
CVH gearbox bolts straight on so no worries there.
You need to find a suitable hose that will fit the larger zetec waterpump outlet.
You need the later mk6 escort top hose with the fan switch fitted to it.
Earth the negative wire from the temperature sensor to the engine as the cvh engine has a aluminuim housing and thus is the earth whereas the zetec housing is plastic and therefore needs an earth.
Cant remember anything else being needed but im sure theres a few people who can either add or change what ive wrting above for you.