Noel someone just pointed me to your post looking for seats. What GT40 do you have? I have the original seats out of my 1984 GTD, which have just been completely refurbished and covered with leather to the original style. These seats have runners on them, and would not be suitable for anybody over about 6ft tall. I have made new ones bolting directly to the floor.
I've attached a pic so you can see what they look like. I note you're in the US. I'm in Australia, so getting them to you might be a bit problematic.
Regards Brian Wilson