Machining Air Grabber Turn Signal Openings

[Moparfiend]

Anyone here successfully opened up the Air Grabber signal opening in the cast material of the 70 hood? If so what did you use and your experience?

I unfortunately no longer have access to the Bridgeport. So its going to be air grinder and file?

Is this stuff magnesium?

 

[dadsbee]

Haven't done so, but my "go to" would be a Unibit.