Can a Sti Motor, tranny and diff. fit in a 2001 Subaru Legacy GT? It would be really helpful if anyone knows about it coz l am thinking to swap my engine. Thanks
Thank you for answering my question; I am sorry, I am really a newby into this car thing and l have another question.

What is the difference if l will swap my legacy GT Motor/engine into a WRX one rather than a Sti? Will it be less complicated?

Go to the NASIOC (North American Subaru Impreza Owners Club) website & read around. Google Subaru - chances r pretty good that the enthusiastic following behind Subaru has at least a few knucklebangers that have done this swap & can point u straight.

Subies r pretty good about swapping parts back & forth, so at a first guess without researching, I'd say it should not be too difficult to do, as engine swaps go.

UPDATE: You want to swap a less-powerful engine into an STi? Why? Talk about sleepers, that'd be a zombie.

The complexity would be about the same going either direction, more power into the Legacy or less into the STi.

It has been done but depending on the year, it could be a lot of work. You need the wiring along with the ECU & completely rewire the car. Plus if u use an 05 or newer doner, u need the guages too because yours will not work with the 05 & newer ST l ECU. Also if u get the drive train out of an 05 & newer, u also need new wheels because the bolt pattern will be different. It would be ideal to find an 04 doner but that could be tough. Or just go with an 06-07 WRX swap. Easy to get ST l power out on those engines but for a lot less money. Then just upgrade ur gears or fund any 6 speed ST l tranny & u just wont be able to use the DCCD but have a strong enough tranny to handle the power. There is a lot more to research so like the guy above said, check out NASIOC or rs25.com on swap info. Or just look for a reputable tuner in ur area that does swaps & ask a lot of questions. A good shop will take the time for a potential customer.

Most to all of the Subaru Engines/Drivetrains r pretty interchangeable. But that is a very involved process ur talking about. For the whole STi setup to fit into ur Legacy ur looking at the ENTIRE drivetrain(Tranny, Axles, Rear Diff, Brakes & Hubs/Wheels) Then the motor would probably require some new cross members(at least) so the exhaust could be routed correctly. The wiring harness/ECU is probably the most time consuming thing out of all of it. I've heard 40+ hours just of wiring to get the harness swapped over, & that is not even changing gauges & whatnot on the interior of the car.

You're looking at spending $10-20k to do this, even if ur thinking about doing it all yourself. Best case scenario u got a donor car, which will run u at least $8k for something u can use everything out of. Its a great idea, but an enormous undertaking.