hello,
engine can be the same if its the V8s, the sedans got the 2,6l I6, 2,8l I6, 3l I6, 3,8l V8, 4,2l V8, 5l V8, 5,6l V8
the coupes only have the V8s, no I6 engine in those.
there are a few parts like some of the interior parts, and the taillights interchangeable from the SE/SD/SEL/SDL/SEC but the headlights and corners and A LOT of other parts are NOT interchangeable from sedan to coupe.
hope i could help ya[

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