[mullrat]

I think Hartage put the M5's V10 in a 3-series sedan. They had to make major mods on the dash and suspension. It will not happen because it will break bmw's holy grail which is 50:50 weight distribution. That's why they went with a high revving light weight engine, rather than something heavier like the v10. Don't rule out slightly higher displacement or ECU tuning to produce slightly more power.