Yah, round file or weld shut completely and re-drill.

Why not just drill a bigger hole on the wrong piece? Will that work for your application?

Something like this?
https://www.amazon.com/gp/product/B00JL4F1SM/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

The way we used to take care of situations like this where I last worked is like this:

http://forums.pelicanparts.com/uploa...1487607103.jpg

Figure out what the next size up is that covers the off-set hole, line everything up as per my above post and drill with the larger size drill bit. The drill will follow the original hole and when you're finished the offset hole is gone but you have a shear tight alignment of both pieces.

Does this bolt onto something else? Are the holes in their positions because they need to match holes on another piece?
If not, just start over. Bolt the thing together with the outer bolts, and drill a new through-hole near the existing hole.

Get a 6mm 2 flute end mill and use a drill press to plunge through the bolted together assembly. The flat bottom of the end mill will minimize elongation of the correct location hole you are using as a guide. I'm assuming you don't have a mill...

I'll offer up another solution. Plug weld the wrong location side, then drill it out from the back (correct location) side.

Definitely need to post some "after" pictures.
No pressure!:D

Scott saves the day! All suggestions were good, thanks to everyone. Scott's was the most expeditious, thank you! Took a half hour.

Clamped and Drilled
http://forums.pelicanparts.com/uploa...1487631323.JPG


Dressed with some HF mini files
http://forums.pelicanparts.com/uploa...1487631323.JPG


Bolted through easily
http://forums.pelicanparts.com/uploa...1487631323.JPG


Other side is tapped for ease of repeated loosening, tightening
http://forums.pelicanparts.com/uploa...1487631323.JPG


First grille to do
http://forums.pelicanparts.com/uploa...1487631750.JPG

Glad you had success Shaun!
You're welcome.