You can search forums until your head turns blue on this topic. I am leaning towards the ProCar Rally seats for the 67 as they give the right look but offer more support and importantly the safety of a head rest. A lot of the aftermarket seats offer ready to bolt in seat tracks. But I know a lot of 2nd gen guys just unbolt the seat tracks from their sets & bolt them to new seats, mostly 4th gen seats.
I read a lot of guys looking at these:
http://www.motorsportseats.com/procar/rally.html Mostly ProCars, Corbeaus and Recaros.
http://www.arizenracingsports.com/pa...ts/ArizenBlk-S
I saw a few interesting threads at TGO, but it is down right now. Audi TT seats was one set. Another one had the GTA logo stiched in, look real nice (maybe the Arizens).