GTO seats will fit in a 4th Gen. I repeat, WILL fit in a 4th Gen.
I don't know why everyone says they are too wide, they are nearly identical in cushion width. Yes, the rails are wider and you will have to trim the bracket on the rear rail (closest to door sill) to get the seat to sit down properly. The mounting locations are far different and will require the fabrication of an adapter bracket.
Examples:
http://www.ls1tech.com/forums/appear...gto-seats.html
http://www.cardomain.com/ride/2281318/2