If the mount is metal, you will need machine screws. If it's a composite, you will need sheet metal screws. Dubro and Great Planes make both in a socket head configuration. Use #4 for anything up to a .45 and #6 for larger engines. Be sure you drill the proper size pilot hole for the sheet metal screws and the proper clearance hole for the machine screws. With a composite mount, use a little lube (I like white lithium grease for various reasons) on the screw the first time you turn it in.

Dr.1