Listening to all your comments, I shoud stick with a manual.

You are probably right about the sluggisch BW35 but I just love driving an automatic.
Here in the crowded Netherlands we have a lot of trafficlights, ‘speedbumps’, crossing, and roundabouts. The highways we have are just about every morning and afternoon stuck with traffic jams. So driving here is a constantly changing gears with a manual.
In contrast to america 95% of cars here have manuals, but more and more people choose for automatics nowadays, simply because it gives a more comfortable ride. I do agree its not as fun to drive, but if I would just want ‘fun’ I’d buy a quad or something.
I know it’s a lot of work (I already put a M46 gearbox in my other P130, so I know all about changing tunnels etc) but I will proceed. The combination of the smooth automatic and the overdrive, and a B20E will give a nice drive I figure. The AW71 overdrive has ratio 0.69-1 where the M41(and M46) have 0.79-1. So the engine will have even lower rpm’s. (neglecting slip in torque convertor) Or I can even buy a AW71L, so the torque convertor is locked at higher speeds. I might even use a rear axle with a lower ratio (3.7-1 in stead of standard 4.1-1) from a 240 series, although that might be just a bit too much.

Although not original, I still thing it will be perfect to drive.
Ben