Thanks for the advice on the self tapping screws.

Don't think I was clear, the problem is that all my other engine mounts are flat on both sides, so that you can mount the engine on one side and bolt it to the other. But because this mount has only one flat side I didn't think that bolts would have anything to grip, therefore would fall off quickly. I was concerned over self tapping screws, and wanted to make sure that they are safe to mount an engine with.

Thank you again for the help with the self tapping screws.