Pretty sure TJ's on the money here. That'd be the 71 model year when the 3.0 engine was introduced to the E3 and E9 platforms (3.0CS E9, and 3.0S and Bavaria E3's.) I don't recall ever seeing a factory-built street 3.0 (E9 or E3) with a ZF 4-speed trans in Hoffmann's US market. And I don't recall ever seeing any '68-'71 2500 sedan, 2800 sedan or 2800CS street cars with a Getrag in the US market
edited, after forgetting the board has international readers. I can only speak for US market, and only for cars I have personally seen here,
I rather liked the ZF's, even used ZF 4-speeds a few times for Auto-trans-to-manual conversions, on mostly Bavarias but a couple of coupes also. A lot of people cannot stand them but I think they're kinda snick-snick cool shifters in a slightly un-refined way. Getrags can be so pedestrian! 8)