on top you'll need the sway bar modified to clear the sump as the 2tg powered te27's have a different sway bar.
probly the best site for 3tgte into E2 corolla is toms site
http://www.netwiz.net/~tcar/corolla.html
also 'the red rocket'
http://www.onthenet.com.au/~paulp/corolla/
or check out some of these links
http://www.arfabuck.orcon.net.nz/links.html
you can get away with using the later model 22spline T50 box with not much more than 200ponies. they're found on late '82 and '83 corolla te71 and 83-85 ta61/63 celica's. the ke25 gearbox crossmember can be moved back a set of holes and the t50 bolted in, then use the position to make engine mounts. find a larger driveshaft to suit and shorten it. a 4spd T40 box has 22spline yolk too. a w55 from the 3tgte will fit with a little panel beating of the gearbox tunnel but requires a custom gearbox crossmember also. theres not much room for an exhaust past the crossmember either. ul need a diff conversion coz the little std one wont last. at least go for a T series 6.7" diff minimum. these are narrow enough that will fit if fwd offset wheels are used or get flares fitted. id suggest a shortened toyota F series 7.5" diff if you can afford tho just to be reliable. ive snapped a couple of T series diff axles with the T motors. expect to pay quite a bit to complete the whole conversion properly and certify it. along with bolting the engine you need to consider ecu and loom, radiator, intake, exhaust, brakes and high pressure fuel system. the brakes for instance wont fit a twin master cylinder because of its positioning too close to the intake manifold. also they dont have a brake booster so using larger brakes could affect the pedal effort with the single brake master cylinder.
the weight of the 3tgte (close to 200kg) is another thing to consider. it wont handle as well as a lighter engine. a 4age is another consideration but is a similar amount of work to install as the 3tgt and less power. then a whole different story to turbo a 4ag(z)e properly. (which id prefer over the 3tgt in a ke25).
roy fordelsen has a te71 with 3tgte, now with T3 turbo 14psi boost, supra intercooler, bov etc but still using std T50 and T series open te71 disk brake diff. the te71 with that running gear will weigh around 1000kg compared to your ke25 which when done would weigh about 150kg less. so running gear would last a bit better.
the T engine is one of the more common engines to convert apart from a 5k. they came factory in japan with te27 chassis and the twin cam 2tg + t50 and T series diff so the E2 corolla is designed to fit a T engine. in usa they had a 2t-c pushrod.
some pics on roys te71 here
http://www.arfabuck.orcon.net.nz/Gallery/Royte71.htm
oh and the early ca18det had less factory power than the factory 3tgte. the later ca18det a little more..
each engine has potential tho... ie the 3tgt has no intercooler, no BOV, a shit turbo and rich tuning... so fix those bits with an injector and fuel pressure upgrade and your lookin a 250+ horsies with the correct tuning. oh and a downside of the 3tgt is its age. its a 21yr old engine will need a reco if it hasnt already. you should be able to pick one up for around $700 with box and loom. keep an eye on the T&E.