Thank you for the response, Chris.  My point in asking the question was I was thinking about the originality in the cut out in the hood.  If it was home made, I wanted to weld a correct panel back into the hood.  The tab that the arrow points to could have only been to hold the panel that was cut out of the hood.  

The reason I'm thinking this is a factory cut is because there is no sign of saw marks.  The cut is perfectly square.  You can put a carpenter's square into the corner and it fits perfectly.  The hood is not warped in any way from cutting.  That is why I think it must have been done at the factory.  

However, now I realize it really doesn't make any difference.  Whoever did it, did such a good job I am going to bolt a panel back into the opening.  

Also see my same question on the Oliver Page.  

Thank you again for your comment.