I checked the difference in weight between the motor of the M5 and the 528 with the local dealer service manager (who is also a great guy and the president of the local BMW chapter). Seems the difference in weight between the motors with all their gear is about 50 pounds - which is not much. I guess I could go on a diet!!! We are purchasing all the appropriate camber plates for the M5, so I will keep you posted. My first car was a 1971 Dodge Charger R/T 440 Six Pack. We eventually swapped the motor from that to a tried and true 318, but kept the R/T suspsension intact. I did not notice any difference in ride with the difference in motor weights there, so we will see. I am also changing to 540 Sport wheels/tires.