I have attached a diagram from the MB epc - lower left should be like your car. Item 200 is line from tank to damper and then into pump suction.

Is the Airtex pump a rebuilt exactly same as original? I seem to recall they also had one with an external rubber sleeve that would fit, but likely did not have the internal relief valve.

Unfortunately it is very expensive to get the right pump. I eventually found a new one in stock for about C$500.

(Posting the info below for future reference by me and anyone interested!)

Some other cars use the same pump - I think one of them is an early Nissan ZX but others are Opel, Saab, etc. Bosch pump number is 0580464005 or 61405. There was a pump for sale on eBay and the auction listed that it was applicable to these cars:

Part number 0580464005

APPLICATION GUIDE:

MERCEDES-BENZ 280SE (1971 - 1972)
MERCEDES-BENZ 280SEL 1971
MERCEDES-BENZ 300SEL 1972
MERCEDES-BENZ 350SL 1972
MERCEDES-BENZ 450SE (1973 - 1975)
MERCEDES-BENZ 450SEL (1973 - 1975)
MERCEDES-BENZ 450SL (1973 - 1975)
MERCEDES-BENZ 450SLC (1973 - 1975)
NISSAN 200SX (1980 - 1983)
NISSAN 280Z (1975 - 1978)
NISSAN 280Z 2+2 (1975 - 1978)
NISSAN 280ZX (1979 - 1983)
NISSAN 280ZX 2+2 (1979 - 1983)
NISSAN 280ZX 2+2 GL 1981
NISSAN 810 (1977 - 1980)

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5