That is a really nice looking interior already, whats the plan?
I have been thinking about keeping an eye out for one of those to play with...
It needs carpet. My center console also has a crack in it by the power mirror switch, and I have it's replacement already. The drivers seat has a tear (you can see it in the pic). So, I am going to reupholster the seats. I actually have a set my buddy gave me out of his 90 I might use those instead, but still reupholster them. The 87-89 GT's have a piece that pulls out for the back of your knees to rest on. All it really does is make a spot for dirt and lint to collect. I would take seats out of an 85-86 GT over anything though.
They are very fun cars to own. I've owned three (this is the second one I bought) and had loads of fun in them.