At 8 months old I think they are still trainable but make sure people know that he doesn't like strangers. Tell them not to look directly into his eyes and not to approach him. You didn't say that he was aggressive outside while walking or inside your home, but if it's in your home then put a "treat jar" near the entrance and when people come in tell them to get a treat if they want to talk to him.
There is much more information on Cesar Milan's website about agression. You can just google his name to find the website. You can also watch his show on The Animal Planet station on cabletv.
You can train him slowly but you also need to train people how to act around him.