I believe the back portion of the seats is different although I am not positive of this. the back seats in these are useless for anything other than a baby or very small child, better to give you more storage in the back and get rid of unneeded weight. but I can seem to find anyone who sales one of these for a convertible.
Funny enough, I moved from a series of two seaters to this GT specifically _for_ the rear seats We have a 9 year old (8 when we bought this), so figured we'd have a few years of her not being too big (this is for short trips around town anyway).
You know what you could do, is check out the part numbers of a Ford parts site for the rear seat assemblies - you might be able to get a sense if there are any part variations for coupe vs. vert, then if they're all the same, you'd probably be pretty safe with ordering a coupe delete product.
Hey, go up to the photos thread and check out post #1738. Robertsimpson posted a neat photo with the seats removed. No bracing really and looks pretty straight forward if you wanted to mod or do your own delete.