For another option, check out Rockauto.com. They had Upholstery (not seat covers) recently for a good price. With the 5% discount does, and shipping, you can get them for $370.
If you are looking for Grey, I have a GT set I just pulled off- no tears or rips, but some accumulated dust and dirt- $150 shipped. Will be posting them in the Mall soon- just need to get some pictures taken.
'87 GT in process!