There is no inexpensive way to refurbish the seats that lasts long term. I have seen no good grey seats in the yard. The one outstanding possibility was stripped before I saw it. Mechanicals let go will still add up for parts only. You can scour the yards frequently - if you have the time and do it for fun without putting a price on your time.

I have about 4K in parts in mine over several years and started with a car that has been in the family since new and maintained by dealer and expensive indy. Much is considered maintenance but I haven't driven a lot of miles. It still needs paint and AC work.

You can also drive a ragged out old car and fool yourself that you are driving a fine German product. The product is fine. Your example will still be a ragged out clap trap until brought back to specs. Sellers think bottom dollar is $1000. Perhaps it is for those that need transportation and will live with things not working. A ragged MBZ is better than a ragged honda.

Salvage price on an SD is $250 - $350 retail. I shoulda bought the $5000 example that needed nothing (obvious). It would have been less expensive than the $500 car that is too good to part. I pulled the ccu hoping to install & it needs soldering so even the parts can't be counted on.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.