re: "...the 1990 300E is the slowest one of all time. It had the 90+ axle and gearing with the pre-90 2nd gear start. ..."
Not so -- they didn't change axle ratios until they adopted the "start in 1st" transmission, too. And, it sounds like you never really tried the '90 300E. Although its default is to start in 2nd, it has a lower axle ratio than later models -- later on, they combined the start-in-1st transmission with a much too high axle ratio -- no real advantage -- actually, if you try a little math, you'll see that the combination of the 2nd gear and axle ratio of the '90 version is within a mere 7% of the combination of 1st gear and the axle ratio of the later version.
And, if you flick the shifter to 2nd (to engage a smooth 1st gear start) in the "old" setup, you can combine that 1st gear with the much lower axle ratio for a really MUCH lower overall starting ratio -- in other words, when you really want a lot of torque multiplication, the '90 setup is far superior to the later models.
The only weakness is, of course, the 177 bhp M103 engine -- the later M104 takes care of that limitation, with 4-valve, variable-valve timing, and two different intake plenums, combining for a much flatter (as well as higher) torque curve.