Buy a set of tap and dies in metric. Every screw needs to be threaded and holding. You WILL LEAK OIL unless you repair them.
If the stock size tap will not properly re-thread those holes, you'll either have to heli-coil them or timesert them.
To properly tap, get the tool centered on the hole, and still. Spray the tap with some cutting fluid or dip into Marvel Mystery Oil. Turn in 180*. Turn back 90*. Turn in 360* from there, turn back 90*. This in-and-back helps pull any cut debris up and out of the hole along the tap. These holes are into aluminum, so it won't take much force. Don't screw it in straight away to the bottom and try to be quick.
Turn in, turn back, turn in, turn back. You'll be cutting near perfect threads and preventing any oil leaks.