Changing a Lawnboy "C" series engine to "D" series piston and cylinder?

It is my understanding that one can change a "C" series engine to a later "D" series piston and cylinder. From what I have read, one has to also change the connecting rod. My question is, with a "D" series connecting rod, piston and cylinder, is that ALL? Will the "D" series con-rod fit the "C" engine crankshaft?