patina haters gonna hate......Wow the car turned out quite beautiful! I would re-cover the seats with the original black/black color. You've worked so hard to make it original, there's no sense in going for a kustom color look on the seats at this point.
With 30-year old leather, all of the attempts to restore the original covers end up disappointing. They look good in pictures, but when you get close up in person, they still have that "tired" patina. The new leather really pops.