I've dug up some random specs on a few MB's regarding curb weight and static front/rear weight distribution:

According to April 1981 Road & Track:

1981 300TD wagon (w123) - Curb weight = 3,805 lb.
weight distribution front/rear(%) 52/48


According to April 1986 Road & Track:

1977 280E sedan (w123) - Curb weight = 3,565 lb.
weight distribution front/rear(%) 54/46


According to Jan 1987 Road & Track:

1987 300TD wagon (w124) - Curb weight = 3,715 lb.
weight distribution front/rear(%) 52/48


According to April 1986 Road & Track:

1986 300E sedan (w124) - Curb weight = 3,220 lb.
weight distribution front/rear(%) 54/46


According to January 1981 Road & Track:

1981 380SEL (w126) - Curb weight = 3,815 lb.
weight distribution front/rear(%) 54/46


According to November 1971 Road & Track:

1972 280SEL 4.5 (w108) - Curb weight = 3,775 lb.
weight distribution front/rear(%) 56/44


According to June 18, 1970 Autocar:

1970 280 SE Automatic (w108 w/6 cyl.engine) - Curb weight = 3,450 lb. (in Euro trim)
weight distribution front/rear(%) 51.5/48.5

It would appear that diesel wagons are not only significantly heavier than their gas-engined sedan counterparts, but a static weight distribution comparison indicates the wagons are a little more tail-heavy than the sedans, even though the wagons are equipped with turbodiesels which I assume (and correct me if I'm wrong) were heavier engines than the 6-cylinder gas engines.

I threw the w126 and w108's in for laughs. It's interesting that all of the post-1972 sedans outlined above have the same weight distribution. Coincidence, or design philosophy?

In my teens, my family owned two 1978 full-size GM cars, one a wagon, the other a sedan, both with the same drivetrain. My idea of a good time was to pack either of these cars with a few friends and whale the crap out of them (both cars and friends) on a very narrow, winding country road. (Clever, huh?) I remember having a significantly easier time swinging out the back end of the wagon on a tight curve than I would with the sedan. I assumed then that a difference in weight distribution played a role in the handling differences encountered.

I believed then, and I believe now, that most station wagons are more tail-heavy than their sedan counterparts.