No for the rear. Mine we just "ok" but functional. The top of the back seat was a bit dry rotted and it was musty too. I pulled out all the hard dry crap I could and put in upholstery padding you can get at fabric and upholstery shops. After thinking about it I realized that only very rarely would someone be in my backseat, so I did not do a lot of work on the padding in the rear. I did look a bit for new rear foam etc and could not find rear anything. I don't think they are available new.
I'd say for most e-bodies that 95 rides out of 100 are front seats only. At least that's the track record for my car which I've had since 1980. So unless you have water, bad sun damage, or a mouse/rat problem (which I have seen for cars left sitting a long time) you could clead, freshen, repair and reuse. I'd just carefully disassemble, take lots of pics and clean them best you can if they stink. Use the pics to get it back together. If the underneath is functional, new covers will.....well......."cover" them.
By the way after I bought all the Legendary parts (foam pads and covers for front and rear) just to check, I called three local auto upholstery shops to see what they charged to install this, thinking if it was reasonable I'd get them to do it. Best quote was $800!!! To me NOT reasonable at all. Fact is I did all of it in about 3 days working evenings. Now after learing on my car, I could do a whole Challenger from bare frames in about 4-6 hours now. If I had the volume of work for $800 a shot, I'd quit my job do that full time.