if this mod was so cheap and easy im sure there would be more than a few running around right now. stuffing an all wheel drive drive train into a small front wheel drive platform... yeah.... sounds cheap to me, go for it

 

here is one of the best kept secrets for rebuilders.very cheap wrecks and they have lots all across america.You have to sign up for a guest membership(free) but check it out and if it helps let me know
www.copart.com

 

ok the link you posted with the black wrecked sti, that engine and tranny are both toast. it's it's not like throwing some components on them is going to fix them.

engine management what are you looking at? there are a lot of good fully programmable opensource software out for scoobydoos but the megaquirt coding hasn't been cracked for them (well i've heard about 2 months ago it was but it hasn't been confirmed). So you're looking at running Hydra, a great system, but that's $1700 for engine management right there, and that's before wiring, as you don't have the needed sensors, harnesses and connectors yet. You're looking at $4000 just in engine management.

and why are you so deadset on the sti motor? just use any EJ25, send the heads off to get port and polished while doing the swap and get some cams for it, there are a lot more cam options out there for teh non-avcs heads anyways. turbowise, swap in a clipped 20G from the get go, unless you want to go twin scroll from the start (which is what i would do) but then you're looking at $5000 for the turbo (i'd go with the gt30r in this case), equal length header, divided uppipe, EWG and turboback.
And we haven't even started on about tumbler deletes, Y pipe flow and the fun of that on the scooby engines on the intake side...
or intercooler setups...

or suspension and chassis fabrication and reinforcement on a putting out 3x's more power then it was designed for. or a tunnel for the rear axle shafts and differential housings.

you can easily spend $15,000 on correcting engine and suspension issues on an sti itself while it's still in an sti.

i'm not saying that it can't be done, and i'm not saying don't do it but you're looking at $25,000 in PARTS to get it done RIGHT( suspension components, differentials, engine, transmission, harnesses, ecu) and about 600+ hours of labour.
That being said if you have that type of resources at your fingertips go for it.