I've had the tape measure on the one in my dad's 840Ci Sport - it would go in I think but it would probably need a bulge on each side at the front
Although shorter than the M20 its very wide.
Still with a manual box that would be sweet.
It pulls 2 tonnes around very easily, especially on kick down. So it would be enough to scare the living brown stuff out of you in a Sportster sized car!
The sound it makes although subtle is awesome.
It amazing when your doing over 100mph push the pedal far enough to activate the kick down switch you get almighty shove up the back side as it drops down a few gears! At 80 the engine barely gets past idle.
I wish I could afford the fuel to drive one on a daily basis to work.