Velour bench in a Dart ?

Only velour I've seen original in an A-body were Valiant Broughams and Dart SEs. Legendary Interiors doesn't show one. If you like it, don't be dissuaded by me.

Try http://www.seatcoversunlimited.com to see if they have one you think would work as a replacement. They may be willing to do a set specially for you if they stock the fabric.