why was this done

[tet68]

upper left and right corner of firewall very neat rectangular holes look almost factory one has a silver cover on it.no sign of a cage ever being in car however transmission hump has a big hole in it not rust but maybe an exploded transmisson

 

[TrailBeast]

Drain cleanouts that someone cut.
Notice the OEM hole on the outside of that corner between the cowl and fender.
The square holes make it a ton easier to get rust causing crap out.

 

[pishta]

Cowl cleanouts?

 

[spl440]

Either to clean out leaves and junk from cowl or cowl induction for air cleaner

 

[Jamakin]

my duster had those in the same spot, they were made by someone drilling 100 holes and then covering them with sheet metal. I have since welded them shut

 

[marksmopar1]

73-74-75-76 or so A body cars had a vacuum control, part of the emission system mounted on the passenger side cowl where the one hole is in your picture, but on the drivers side I am unsure. The passenger side hole looks about the size of the hole for the emission vacuum control as factory.

 

[TrailBeast]

73-74-75-76 or so A body cars had a vacuum control, part of the emission system mounted on the passenger side cowl where the one hole is in your picture, but on the drivers side I am unsure. The passenger side hole looks about the size of the hole for the emission vacuum control as factory.

My car has the emissions controller you are talking about, but the hole behind it isn't square but in that same place.
I have removed it to clean the cowl out before.
It looks like someone cut it bigger.

 

[chryslerfat]

Drain cleanouts that someone cut.
Notice the OEM hole on the outside of that corner between the cowl and fender.
The square holes make it a ton easier to get rust causing crap out.

This would be my guess.