The motor you have is very reliable and needs very little in the way of break-in. (It's in the owners manual.) I have the very same motor in my plane. I just put it all together and ran about a tank and a half through it with the standard prop. Vary the speed from idle through full throttle and run it just a touch richer than normal. That's it.

As for the motor mount, I don't know exactly what you have but I'd feel better with bolts and nuts. Make sure that the nuts are the captive type and/or you use a drop or two of Lock-Tite on the threads. You don't want the vibrations to loosen your motor. It is a good idea that you do the same to the muffler bolts too.

Good luck.