Catching up on unread threads, and I just saw this.
My w111 is a 250SE/C (so, high grille). When I was searching for a car (circa 2006), I came across a 1970 low-grille 2.8 with a five speed (not ZF). I still wonder if I should have bought it. It was a bit more rusty than I was comfortable with.
I remember searching for production data on the ZF versus MB 5-speed, but found conflicting numbers from various sources. Never went back after all was said and done to check the numbers, so I too would be very curious to know more about the production data.
I'm very happy with my coupe, the high-grille, four-on-floor, and sunroof. The 250 motor is as peppy as ever (with a fresh transmission rebuild and new clutch!). I frequently take it on road-trips and average 80 mph, and it always feels very responsive. These cars are very under-valued, and the 3.5 cars are (IMHO) over-valued. Of course, I'm biased ;-)