With the seat electrics involved separation of the seat back from the bottom is kind of a pita. btdt. Additionally, the seat memory for the driver's seat would require that you interchange the control modules if you want to retain that feature. If your seat bottom is just 'flaccid', there's a much easier fix that'll make a world of difference. After about 04/89, there were installed universally at the factory 2 foam blocks in each front seat. I just last week finally got around to installing those into the seats of my wagon and they completely transformed the seat. It was Dave Meimann I believe who first discovered that this is a factory specified fix for the problem as indicated in the Programmed Repairs section of the fsm in group 91. You'll also find some similar documentation at his website that I believe came from the WIS. Look for 'seat boost' at: http://www.w124performance.com/docs/mb/W124/ & http://www.w124performance.com/images/W124_stuff/.
I said it's easier than swapping. That's assuming you haven't found a pristine junkyard seat with which to replace the entire assembly. You'll still have to pull the seat and a couple of plastic trim pieces and tease the cushion bottom out of the channel in the frame. As it'd been a while since I'd had the front seats out it took me probably 2.5 hours soup to nuts for the driver's side. Couple of days later with that more recent experience under my belt I did the passenger side in 1.5 hrs. If they're not already broken don't be surprised if you do break at least one of those plastic trims trying to get them off; fortunately they're not horrendously expensive to replace. -j
