The M6!!!
We are over looking possibly the best BMW of them all. The M6. I had one. This is a VERY cool car. It has a inline 6 and it was HELLA fast. It is a 3.5l with a MONSTER intake manifold. I was able to do 150mph in mine with NO problem, and the car was a boat. In the US the more popular version was a 635CSi. The car I had was a grey market M6 from Germany. Very nice car. If it is possible to swap heads, Screw that, put the whole **** motor in and get the Alipne kit for it. That was a Turbo conversion done to the M6 and it made it fast enough to take just about anything, exotic or not. My M6 wasted 'stangs, vets, cammaros, LOTS of Hondas, and a 1 Lotus Espree Turbo. I will never forget that face... I had bunches of fun with that car on Westheimer in Houston on Friday nights, took alot of money too.

My goal to to get my Z that fast. The only draw back to that car was its weight. It was heavy.. But If you do find a M6 head and can make it fit, I will buy the motor and slap it in my Z!!! MZ!!!!
Bean Bandit