DUST COVER FOR 727 TRANS,WHAT YEARS FIT MINE

1968 Dart 270 said
Why are there two different types of small block dust covers? The top one has a different shape at the top section and is a solid one piece stamping. The one below it has a removable center panel.
Which is factory correct? Anyone know what the reason is for the differences?

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The untouched before I messed with it 1973 Dart Sport 340 has the one with center panel.
Messed with now for sure
Here it is triple plated. Yes I have the panel pic was before I put it on.