Actually, I don't consider the M's to be that heavy. Sure, they could go on a diet for racing purposes. But considering the M was also the safest car on the road in the 80s (Volvo's claims be damned) you might sacrifice some of the safety for weight savings for street use.
NY State registers my 4 door at 3400#. Accurate? Nope. But considering that NY charges by the hundred on poundage for fees, the heavier it is, the more money they make, so I would say it's a good ballpark. And in line with what U-Haul has 'em scaled at for tow dolly and trailer rentals. (I was told that my Ramcharger is too light to rent a tow dolly to pull around the M-body.) But if it is accurate within a ballpark range that puts it around the weight of my E-body and just 400# shy of my B-body sedan. (Again, all according to NY State registration fees.)
