I have a '98 Legacy Outback and recently acquired a JDM Legacy BE5 front clip with the EJ208 and 5MT. I'd like to swap this drivetrain into my Outback with minimal alterations to the setup (ie, keep the twin-turbo system). The brake booster and clutch master cylinder seem to be the two issues with fitment of the left hand turbo. The clutch MC from an STi and/or the use of a remote reservoir seems to address that fitment issue. But after conferring with the owner of the only other Legacy I know of with the EJ208 swapped in, he can't remember if it was a Justy or GL brake booster that he used. Looking at '08+ STi brake boosters, it appears that may be the solution, if I can find dimensions for it. The added bonus being a better performing brake system with the STi booster and BMC upgrade.
Other mods to date:
-King lifting springs (taller, but @ 20% stiffer than stock)
-Rallitek adjustable rear sway bar w/new front and rear sway bar links
-Brake Performance slotted and cross-drilled front rotors with semi-metallic pads
I live in Tucson, AZ where the roads are rough, and there's lots of trails so the height of the Outback works well. But the mountains make the 2.5 and 4EAT work hard and leave me wanting when hitting the canyons.