All 93-05 imprezas have a 16.5:1 steering ratio
The 04-07 STI and 06/07 WRX have 15:1 steering ratios
Subaru changed the design of the crossmember and steering rack in 2005/2006.
So the only 15:1 ratio rack that will bolt into any 93-05 impreza, is the 04' STI.
If you change the crossmember you can use a newer style rack.
(Any 02-07 impreza rack swapped into a 93-01 impreza will need a custom u-joint.)