well, it would take a whole lot of custom fabrication...
custom motor mounts
an adapter to run a rwd transmission
driveshaft
tranny mounts
throttle linkage
computer control of some kind
and a whole bunch of other stuff to connect the engine to the car and make it run right.
talked ole dude out of doing it today he has a 03 focus thats totaled out and a 93 4cyl coupe ..talked him into selling the focus parts and swaping in a turbocoupe motor to match my 91 coupe turbo 4
ummm, guys it is not that hard, there are a few companies that make the adaptor for the T5 to bolt up to a 2.0-2.3 DOHC focus motor. There are a ton of advntages, lots of bolt ons, better gas mileage, and lots of horsepower for the weight, plus you are keeping the car a 4 cylinder, if you want a 5.0 go buy one, I never understood the people that will spend weeks and weeks and thousands of dollars to convert a 2.3 to a v8 when you can buy v8's cheap. You can buy 2.0 and 2.3 motors for under $500 and their are tons of them stuck in all manner of Ford, Mazada, and Mercury's.
"Ford's silver top and black top Zetec engines have been fitted to classic RWD Fiesta's, Quantums, Mk1 and Mk2 Escorts, Anglia's, Orions, Cortina's, even Lotus Europa's, Westfields, and all manner of kit cars.
Ford (being the sensible people that they are) decided to stick to the same bellhousing pattern that they have stuck to since the 1960s. So for a rear wheel drive (RWD) application, you can use the Type-9 five speed box from the Sierra, plus an RS2000 bellhousing. One simply bolts to the other. Note: The Type 9 has a 1" 23-spline input shaft and the 2000E four speed box has a 7/8" 20-spline input shaft. The MT-75 (Granada) or T5 (Sierra Cosworth) gearboxs also fit on the Zetec.
Zetec crankshafts are already machined to accept a RWD spigot bearing, which again simplifies things somewhat."
Plus you can use modified Range 2.3 motor mounts to install the motor in a Mustang without a lot of fabrication.
I wont say its impossible cause people have done the same thing with SHO engines, I'll just say itll be harder than that being fwd and all. easiest thing to do is to swap in a Rangers duratec with the Focus head. THe focus has a tad morre power than the Ranger.
I've seen several things done to focus's. My boss is a focus freak. I've seen one guy go so far as to put a twin turbo 4v 4.6L with a t56 trans and a 9in rear end. he had to do it on a sedan because the hatch was too short.
I've also seen the ole 2.3L SOHC dropped in one. had a turbo and all. Thing was positively insane. I thought it was pretty cool.
If you really wanted too, you could probably drop a Mazdaspeed 3 engine and trans in one without too much problems.