I did my rail-swap (after installing WRX seats) last night. I have some additional information to add to this thread.
See my previous posts in this thread for why I did the rail swap.
My car: 1997 Impreza L wagon
Seats: 02/03 WRX passenger
Rail swapped: passenger seat (driver seat seems adjustable enough and looks like a mess to swap rails)
The instructions that Daios and Kammi333 were perfect however I ran into 1 problem with the more inside (left as sitting in the seat) rail. The front hole for the 12mm bolt was too far forward by about .5" so the bottom of the seat would not just bolt up to it.
Easy solution: drill a hole...detailed instructions below pictures
Below are some pictures describing what I mean:
Comparing the 2 overall rails
Pointing to the specific hole that is needed
Where to drill
-Follow Diaos's insturctions to the point where you have both the rail/bottom assemblies off of the seats
-Check to confirm you need to drill the hole (kami333 did not note he needed to)
-If you need the hole continue on
-Seperate the left (as sitting)/more inside rail from everything else. This makes working with it much easier.
-I used a square to find the center of the 1st hole and drew a line across the general area where the hole was to be drilled
-Do some carefull measuring and draw your 2nd line for where the hole needs to go
-Use a punch at the 'cross hairs' of where you want the hole. This is so when drilling the first hole the drill won't move across the metal.
-Be sure to start with a small drill bit and work your way up to the size hole you want.
-Once the hole is drilled you can continue on with diaos/kami333 instructions
Notes: you have some "wiggle" room with the hole you are drilling. I'm sure you can see mine was a little low but everything bolted up fine. If you look at the back 12mm hole it is an oval shape so in theory you have some front/back 'wiggle' room too.
Hope this helps anyone,