Metal Cover The Fender Mount off

Up front we have a piece od metal that covers the most part of the stub frame. This piece actually bolts to the frame. The bolt holes are slotted so how do I line it up so the fenders fit the car. I see where the bolts and washers were originally but wonder just the same. The passenger side is not fitting right. The cover has 2 large holes where the stub frame rivets are supposed to fit thru but the holes are off by half of the hole diameter. Why is this so. It appears to have been this way from the factory. Do I need to leave it that way or make a filler piece and open up the holes in the correct place so it fits nicer. Just wondering.