The biggest problem I found in doing this swap is whether or not to remove the bottom pan in the motor. I couldn't remove the bar mount stud that goes into the pan. I tried double nutting and vise grips to no avail. I've since learned that you can take a dremel cutting wheel and grind 2 flats on the large portion of the stud and get a wrench on it. I just left the pan on and finaggled the cylinder, crank, and piston into its position and bolted it down. And there's only 1 position for all these to be in to install it without removing the bar stud.
Aside from that, I'd check the manifold boot for cracks, I'd replace the impulse line and fuel line and fuel filter.
And then search you tube and here and come up with a "happy medium" muffler mod. Somewhere between adding/enlarging perimeter holes behind the deflector and removing the center section altogether. On one of mine, I enlarged existing holes and slightly opened up the deflector. It performed better, but not much. On my ported 039/ms310 I opened up the perimeter, drilled a couple holes in the center depression, and considerably opened up the deflector to about 1/2" × 1-1/4". Somewhat loud but very snappy
