The uprights of my two front seats in my 82 van were past their prime. The
base cushions were still okay but the support material in the back was gone
and had a crunchy feel to it.

I was reluctant to replace with new/used seats as I wanted the upholstery to
match ....so...from the junkyard I got two good uprights ...felt nice &
firm...then simply removed the covers on the replacement seats and swapped
over the covers from my old uprights. - In all a 15 minute job per seat
...that's about an hour in all ...you get faster with the last two !...

0) Take your old seat upright...
1) Remove the headrests
2) pop out the plastic headrest locator pieces.
3) unclip the upright over at the bottom.
5) slide off the cover.
6) Repeat for replacement seat
7) swap over the good original cover to the replacement seat upright.

I've now got good seat with matching covers throughout the bus...

I actually picked replacement uprights with the arm rests ...my originals
did not have that option. I've unscrewed the attachment piece for the arm
rest as I need to refurbish the arm rest first...but I found that my old
covers fit okay onto the 'arm rest' versions of the replacement seats...

Steve