I'm making a list of all the hardware I might want to replace with nicer stuff. The valve cover bolts are M6x1.00, and are 25 and 45mm length. i know that those flat head screws are measured from the top of the screw head instead of the bottom like bolts are, so you *may* need to go with 30 and 50mm screws.
I bought M6x1 in 25mm and 2-45 mm, than bought M6 pan head bolts to do the fenders and headlights and any other M6 bolt under the hood was changed same time. All black and all Allen heads.