Fish or cut bait time
Talked with Stefan after he examined the seats - he says most all the padding has disintegrated which explains the 'flat' feel.
*Philosophical commercial: At least to me, I would rather spend money on a great redone original seat with stock engine than have 100 extra horsepower and a crap seat.*
After looking at fabrics worldwide, the LeBarron Bonney TC-1/EXP-301 pair mentioned is the closest, and should very closely replicate the look, feel and ambiance of the original - of which, no photos seem to exist of the interior in the wild. While not quite as "golden" as Scott's excellent color card, I think this is about as good as I will find.
So, we will resculpt new seat padding, lower the seating height to about pre-74 levels, add a discrete seat heater and switch, and cover in the corduroy and velour per original configuration. I'm doing the best I can to return the car to it's original interior look (mine came with a cloth interior from factory) and having it as functionally comfortable as possible.
Hope this works.