It can be done and is an easy swap (I did it on mine) but there are a number of parts that are needed. A different starter cover, a different airbox (obvious), a metal spring plate that attaches to the top of the transmission to hold the clamshell halves, a locating tab that goes on the left side of the back of the engine, a different crankcase breather tube and a different airbox to carburetor intake manifold. The cylinders are staggered. On the flat airbox so are the intake manifolds. Not so on the clamshell airbox, there is a definite left and right side.
Sounds like a lot but most of the parts are very inexpensive. Even the chamshell airbox and starter cover can be found inexpensive if you just look and wait until you find a good price (that means a lot of cleaning and touch-up paint) Duplicolor makes a spray can engine enamel called cast aluminum that works great.
