I always thought it depended on the options the car came equipped with, such as sunroofs or a hitch etc. Correct me if I'm wrong.
-Zach

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1978 240D Auomatic
Custom Charcoal Gray, Navy MB tex, kenwood/Elemental/Boston/Aura sound,
Shaved antenna and emblems.

1990 Lincoln Town Car, Sleeper/Strip car in progress, 17.75@77mph.