Good question, Alex, but can you clarify what you are asking? At this precise moment I am not recalling a part of Lucretius specifically on this as much as I am remembering Diogenes Laertius and Cicero's criticism. And then as to the relationship between happiness and pleasure there is the "shout" part of Diogenes of Oinoanda and then several instances here in Torquatus.
Can you clarify your question? (Or maybe Joshua or Don or someone can go ahead and respond further as is.)