Ok, update to my search for seat trim.
I found an Auto trimmer Stateside that does original style repro seat covers and trim for most Oldsmobile's, more importantly they have patterns for my '73 Delta front and rear seats.
We have already matched the exact style and fit from their patterns and my photos, but now need to work out what the original colour and fabric is to get a good match with their modern fabric.

The original trim code is 334.
Does anyone have a clue how to decode this trim code to get the color and fabric details?

Thanks in advance for any help.

 

Try the materials search at SMS auto fabrics. They likely have what you're looking for.

http://www.smsautofabrics.com/ajaxsearch.php