As Far as converting engines, you should study your candidate's layout

Carbs above the flywheel are hard to contend with

side crankcase reed valves are awkward

Roller main bearings don't seem to work out as easy as ball mains.

Magnesium crankcases are dangerous to be aggressively cutting on

Look for ease of conversion like can the crankcase be separated from the saw frame and how are you going to mount the crankcase to the plane

is the coil mounted on the engine

is the carb mounted on the engine or the saw frame

Where is the carb and exhaust going to be

What will the likely all up weight be

Do you have a plane for it