Same problem on my Dad's 84 Indy, lid is cracked in the middle, where the members that connect to the hinges meet the solid part of the deck.
We guessed it to be caused by someone slamming the decklid while a screwdriver or something was sitting on the strut tower, not to be a design flaw.
Be interesting though if it really is a problem. I would suggest staying with the later model lid anyway, the 84 lids let a ton of water onto the front of the engine.
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