You sure that's it? The original rear bushings do look different from the fronts. There is no rubber bulbing out one side of the rears, as it does on both sides of the fronts.

Replacements will be bulbous on both sides of each bushing, front and rear.

I don't think this is your sound.

Like someone said, check your anti-sway bar bushings, all 4 of them, 2 per side of the car.

__________________
Cheers!
Scott McPhee

1987 300D