Thanks @Conserv for the mention. The story of my car as told to me by the second owner of 32 years was that HA Boyd, the long-time GM of Manheim BMW, had a customer, a G-man who worked out at Ft. Indiantown Gap, who would buy a new car every couple of years. Boyd is said to have specially ordered the tii loaded with everything -- Schwarz, sunroof, AC, leather seats, passenger side mirror, wooden shift knob -- and went to Germany to pick it up as Boyd's wife had family there. My mechanic, Jack Miller, who owns Jack's Auto & Aero in Bainbridge, PA and knew Boyd personally, confirms the family history. I have attached the original bill of lading that shows delivery to Boyd as well as an appraisal letter from Boyd himself in 1983 that references the leather seats.
I was told recently by an upholster that @bavariaboy connected me to that it was unlikely I'd be able to save the leather which is disappointing if true. If that's the case, I am going the route Steve suggests with new leather and the BMW gummihaar seat pads to recreate the original leather interior.