They will work on any GD chassis, that's for sure. The easiest way to check this is to probably look up the part numbers Subaru has on them, and see if any of them differ. I will also speak with Ron, the guy that makes them and see what his knowledge on the subject is.
Ron called me a little while ago and mentioned that he is not looking for massive amounts of money to make these things. He only want's the $10 per filter, that way it covers his spending on the filters at the hardware store. The reason he wants pre-payment is to assure that people do in fact want them. He said a bunch are sitting at his house still that people asked him to make months and months ago and no longer want. That is what he is trying avoid.