I want to skip right over the week sauce 2.3l and go for the 2.5l from the Fusion. The head on that thing is sweet, way bigger then the 2.3. From what I have read on FJ its the same for the outside, if your going to do the work may as well go for the glory. Plus 175hp is not a bad start, add the big three and you should be right at 200 flywheel hp!
2.3 duratec is a nice engine when its running. but i hate it. so much hassle getting parts for an engine that ford either dont make (main bearings) or being discontinued. u also might be scared of sucking up dry air instead of oil and blowing up the motor.
The 2.5 will present many problems for focus owners, as the cylinder head has VTC for both the intake and exhasut cams, as well as a second oil pressure port that the 2.0 and 2.3 don't have. Also don't forget that there aren't many manufactures who produce internal parts for the 2.5 since it is still in its infancy.
If power is what you're looking for, then I'd say get a 2.3 built with forged internals and slap a turbo on it. You'll be making more power than any other car sold by Ford. [cool]
BTW I will be doing a 2.3 swap into my 09' soon. From what I have found, the main things that need to be changed are the serpentine belt, passenger mount (or use washers to raise it .5"), oil dipstick needs a hole drilled .5" higher, and the intake cam needs to be swapped out for the 08+ style. everything else such as sensors, IM, exhaust manicat, etc you'll pretty much take from your 2.0 and swap over to the 2.3.