I think there was a dealer offering a very similar, if not the same ('new' 107 SL) a while back for £40k or £45k. Was in a MB magazine advert, MB Enthusiast IIRC.
I have a slight feeling it may have been a 500SL though - can check if no-one else knows?
This is the place that sold the £18k 2.5-16 last year
Using the RPI index £35k in 1989 is worth £63k today so each of the 600 miles was potentially very expensive.
Plus of course £35k invested in property shares would be worth multiples more today.If the car was bought as an investment it was a bad one !