I second the more aggressive cam comment, possibly a roller if you can afford it. The comp one there is probably the smallest that you would want to go on an engine of that size.
The trick flow heads are bigger, so for the bigger engine it will let it breath better (212CC vs TF's 240) the stealth has an 80CC combustion chamber and the TF has a 78 so it will bump your compression a bit too. TF's also have the heart shaped combustion chamber which if I remember correctly help with the quench.
but this is all IMO only.... I am sure there are more knowledgeable guys in here to help you out.