I was lucky enough to win a K77 a while back. Looking the engine over, the engine mounting lugs are a bit strange. The two front holes look to be sized for a #6 or 8 screw size like you would expect. However towards the back of each mounting lug are two holes very close together that are rather small. Smaller than a #4 even.
What is the logic behind this? My only guess is the lugs are drilled undersized to match two possible bolt patterns and you drill out the holes that match a pre-existing bolt pattern on your plane.

Thanks, Matt