Always loved that design.
Go for it.
I daily drove a '83 633i for a couple of years 10-12 years ago. IIRC it had around 115K miles on it. I had no significant problems, only non-maintainence issues were crank position sensor & water pump. I sold it to a friend who wanted it for his 16 year old's 1st car. He drove it for another 5 years or so before selling it. The 16 y.o. changed springs & shocks because he wanted to, not because he needed to & so far as I know,had no problems with it.
I say go for it, as long as you're comfortable the car was never flooded. The engine bay looks almost suspiciously clean.
In terms of price, by way of comparison:
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