Hi,

You should use an engine either from a mk1 Mondeo or a MK5/6 Escort because later models of Focus and Mondeo have an electronic fuel pump and will be a nightmare to connect the wiring while with a mechanichal fuel pump you cant go wrong. These engines usually come with an intercooler mounted on top just behind the top cover. If you are keeping it that way then you will have to move the brake servo a few inches to the left and extend the linkage bar if its a rhd.Otherwise i suggest you use a FRST front intercooler and just fit the pipes.It will save you from cutting the bonnet up and fitting an impreza scoop. If you are using the fiesta gearbox it should be a straight swap but the flywheel/clutch and pressure plate won't fit so you'll have to use ones from a Fiesta 1.8d.But watch out!
The standard Fiesta diesel clutch won't take the extra power from the TD so buy an uprated set. I would also suggest a set of Fiesta diesel Front springs/shoks for the heavy load cause the engine weighs a ton. You will also have to fit an air filter cause your old one won't be good. Shouldn't be such a difficult operation though. Good thing about Fords is that everthing matches from one another. Should give you some good cheap trouble free power.Quite quick Andy