I used some 98ish Ford seats - they're 58" wide and fit pretty well.

http://img.photobucket.com/albums/v228/Avette4me/My%2058/seat%20project/firstpic.jpg

I did some modifications, ie removed the head rests and recovered them.

http://img.photobucket.com/albums/v228/Avette4me/My%2058/seat%20project/5-finalskinning.jpg

I wrote up a page on it, but it's been hacked to shet, so it's really no good anymore.