ORIGINAL: Mode One
You will need to raise the fuel tank to accommodate the new-higher carb. level.
I agree with your decision to do this! Why manufacturers have decided to design airplanes with inverted engine installations is beyond my comprehension!! Yes, they seem to work better for 4 strokes, however, I still think it makes life more complicated!
May need to raise the tank, may not. It's quite common for the tanks to be too high for inverted engines. Mounting it sideways may actually put the carb at the right position.
As for why engines would be mounted inverted, perhaps for those of us who don't like seeing a cylinder head sticking out of the cowl. An inverted mount of a 2 stroke can make it less obvious than sideways mounting.