bigBADbenny wrote:GR seats should fit right up, airbag plug is different iirc.
Just swap the seat or body side airbag plugs or buy a set of male/female generic plugs from eBay or any wrecking yard.
Ben is correct, airbag connectors are different.
Messing with airbag wiring isn't something to take lightly - small mistakes lead to explosive results. Ideally, you don't want to cut the plugs off the chassis or the seats, so what you want to do then is to make up a set of adapter cables that plug between the stock Liberty chassis plugs and the stock WRX seat plugs. To do this, you want top cut cables (with plugs) off a set of wrecked liberty seats and plugs off a wrecked WRX chassis, and then solder the two together.
I was looking at doing this for a while, I ended up putting it into the "too hard" basket, particularly after I changed my focus to the track car over upgrading my road car (which I rarely drive any more now I have a Mitsubishi Challenger as a daily now).