[j. d. worthington]

As said, italics are fine for this; you don't even need to do that, as you can simply add "he thought" or "he thought to himself" or whatever other appropriate phrase. You don't even need to go that far. Moorcock used such indicators as parentheses and italics to show not only that particular character's thoughts, but those of others they were picking up in Mother London. Granted, it's a bit confusing at first, but one quickly realizes what is going on is a form of telepathy (or a rather specific sort of empathic relationship) among a select group of people there; simple thoughts of a single character can also be designated using various techniques which set them off from the flow of their speech. Try different things to see which is most appropriate for the effect you wish to achieve....