Thanks everyone, great tips so far. I do plan to eventually have my rear seat reupholstered to match the fronts for the sake of asthetics. Few people ride in back anyway.
I agree that I need to sit in the seats to assess the feel. I am 5'10 and 190 lbs, 34" waist so I'd guess that most seats should be wide enough. I found a local Mustang Parts & restoration store locally, they are a distributor for Corbeau. This will at least allow me to physically inspect something up close.
SEMA? I'd love to go, but isn't that restricted to people associated with an auto related business?