For a 5 speed swap into an SVX the GC Impreza is the best donor vehicle. Either 2.5 RS or ANY WRX pre-1999. The pedal box, mildly modified, Clutch cable, gearshift lever, along with the rear diff gears will be needed. There's a GREAT writeup here: http://www.subaru-svx.net/forum/showthread.php?t=54258
This is written by the acknowledged "originator" of the 5spd swap into an SVX, and is widely accepted as THE swap bible.