Putting your child to bed later will not fix his early rising promblem. I would put him to bed EARLIER! I know it sounds crazy, but it does actually work. I put both of my kids(19mos and 3 years) to bed around 6:00- 6:30 and they wake up between 7 and 8! All though your son might always be a early riser, at least he will be well rested.
Healthy Sleep Habits, Happy Child is the book that I read when my first daughter was having sleep promblems and it really helped a lot. My second daughter is an amazing sleeper (2-3 hour nap and 12-14 hours at night)and I attribute it to this book. Sorry I don't have the authors name as I am lending it to a very tired Mommy!!!