Dave,
I made a terrific tool for locating bolt holes in engine mounts, at least in the fiberglass or composite type mounts. It's called a piece of bent wire that fits loosely into the engine lug's holes. I place or clamp the engine where I want it, heat the end of the wire, and slip it into the engine mounting holes one at a time.

When you remove the engine from the mount, you have perfectly spaced pilot holes for drilling. I haven't ruined a plastic type mount in eight years.
Dennis-