Hi!
All you have to do is to glue the engine to the mount using Ca medium glue and use a long drill and tap one of the holes! Then remove the engine ,which is easily done, and screw the engine firmly to the mount .
Then...drill the other three holes (the engine still atached to the mount) and tap the holes.
3,5mm -4mm diameter screws are adequat to use for a .72 Engine.