What traits of Huckleberry Finn's character would Ben Franklin approve?

To best answer your question, I will refer to Benjamin Franklin’s journal entry “Plan of Conduct” as a guide for pondering what qualities he might have admired in the fictional Huckleberry Finn.
One of the tenets of good conduct, according to Franklin, is to always speak sincerely, being careful not to lay out expectations that an individual is unlikely to meet. Huck certainly follows this guideline. After discovering that Jim has been sold by the King, Huck can’t even bring himself to pray for forgiveness for “stealing” the Widow Douglas’s property, because he doesn’t actually feel bad about it. Rather than caving to the expectations he was taught, Huck recognizes the truth of a situation and refuses to pretend otherwise.
Another one of Franklin’s admirable traits includes focusing on the positive things about people, even those in whom one could easily find fault. Huck embodies this quality exceptionally well throughout the novel. The biggest example of Huck’s capacity for empathy comes near the end of the text after the fraudulent Duke and King have been tarred and feathered. Even though the two conmen have done nothing but lie to Huck since they met, Huck can’t help but feel sorry for their poor treatment. The King even sold Jim, who had become a sort of surrogate father figure at this point, just so he could get drunk. Huck certainly has personal reasons to delight in their misfortune, but instead he sees their punishment as evidence of man’s capacity for cruelty. He even tries to prevent their being discovered as frauds.
Huck Finn demonstrates both of these noble traits throughout the story, of which Franklin would likely approve.