The 370Z is more of an evolution thtn a revolution in design. EVERYTHING was improved a little bit. The only exception was the 2004 1/2 350Z, it was
FLAWLESS!
The weight confusion is that in 2006, the 350Z gained 150 lbs. So the early 350Z's with the less powerful engine (DE - 283 hp) actually weighed less than a 370Z and the post 2006 Z's with the more powerful engines (revup and HR - up to 306 hp) weighed more than the 370Z.