I've changed Naruto's bounty on A pirate's life for me! Thing is, I am not all that knowledgeable in bounties, so I can't figure out what's high or not. So sorry about that.
Just know that in terms of power, in the top 20's list, Naruto would be at #15, and that's only at his base skills. At full power, he would no doubt be at the top 5 most notorious pirates.
Naruto has been trained by legends, and you will see who later on.
So, his bounty was changed to B 950,000,000 in berries. Though I think that's pushing it as in OP, Portgas D. Ace's bounty is B 550,000,000, the highest known in the series.
Still, we never DID see Whitebeard's bounty, so there might be even higher bounties.