I want that height adjuster in the Prius seat. Jelloslug and another guy did it, I want it too! The height adjuster is about 1/4 circle, so you pick up some legroom as well as seat down a couple inches. $125 from local junk yard. Got lucky, this one's in very good shape far as I can tell. Not much rust and mechanically great. The 07 Corolla it came out of .... OMG!
Good luck with the retrofit. You can find instructions on how I did it (back in August of 2005, time does fly!) at: Prius Documents - Folder Shared from Box.net - Free Online File Storage
This would be a very difficulut do-it-yourself modification. I started working on the Corolla seat but soon realized the job is above my skills and time available. I see another option to have the seat rails remounted on the existing brackets which I'll talk about in the mods section.