Yes that sounds about right but 91 has different suspension and 30 less hp .
There are lots of 3.6 liter cars as they were sold in north america but they had 4 hp less than the 3.6 euro car. the 3.8 s were never sold here.
Basic history here http://en.wikipedia.org/wiki/BMW_M5
The car is listed here, it is the only avus blue of this year in canada