I ran into a difference on 66 GTO vs. Chevelle.  The basic pan was the same, but the GTO trunk was longer-there was essentially a flat extension between the bumper and the Chevelle size trunk pan.  The GTO had been rear ended slightly and that section was wrinkled, and it wasn’t included with most A body trunk pans-1 or 3 piece.  I think I ended up buying a correct “long” 1 piece pan from Ames.
		 
		
		
		
		
		
		
		
		
	
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