I was lucky enough that my last two flights on the domestic 767-300s had the leather interior. The seats are thick, but not very tall. Ever since Delta has announced they will be installing the new seats and PTVs, it seems that the mods for the existing seats has halted. I believe only 45% of the fleet actually got the mods.
Here is a photo of one of the domestic 767-300s with the old seats in leather:
Photo © Alex Pan