Hi Barry,
Basically the Lawn King was a shop branded version for chain stores of the Model 45.
It gave you a smaller engine, Pram style handle bar and a bright Pacific Blue paint job which differentiated it from the normal Scott Bonnar machine. It was cheaper than the standard Green Scotty. There was also a "Craftsman" which was much the same thing.
Mechanically it's all the same.
Cheers,
BB.