The engine mount beams need to allow the engine to seat perfectly with no force applied. It is easy to distort the case enough to cause poor performance, early bearing failure, or seizure is the fit to the mount is less than perfect. File the inner edges of the mount beams until the fit with the engine is perfect. Have faith that a good set of deeply rooted screws will work OK in that mount. I don't like to use plastic mounts for these larger engines, but there's thousands of guys who do use them with success.