The breather covers aluminum screws are M5-.80x16. Not sure if there is a grade on these but for sure they are 1x use only. Any amount of excessive torque will wring the head right off the screw.

I ordered a set of these from a Chrysler dealer some time back. But I don't recommend anyone doing that. The screws Chrysler substitutes are anodized steel and are 18 mm long rather than 16 mm. That extra 2 mm length gave me issues during re-assembly. I ended using marine grade steel bolts that have an anti-corrosion covering on them. Makes the screw compatible with the alloy valve covers.

Lots of discussion in another thread on this repair: Valve Cover Leak. onehundred80 discussed galvanic corrosion in this thread and I think he hit the nail on the head with this point. Would explain the selection of aluminum screws by M-B to avoid this longer-term issue. And that goes for using Stainless Steel versions also. If one uses steel screws, I'd strongly recommend a marine grade screw which has an anti-corrosion coating.