Another to compare
https://losangeles.craigslist.org/lac/cto/d/los-angeles-1975-mercedes-benz-450sl/7697599353.html

Seems like these are plentiful, especially if you are willing to get a post 1975 and deal with getting a smog check.
https://losangeles.craigslist.org/sfv/cto/d/valencia-1978-mercedes-benz-450sl/7704785751.html

Also, this is not a commentary on the car you are looking at, but I think these are of the type where you can always buy better and the price is soft. What about 560SL?
https://losangeles.craigslist.org/wst/cto/d/redondo-beach-mercedes-benz-560-sl/7705090195.html