Exercise, exercise, EXERCISE! Labs are chewers and they can be high energy depending on the breeding. He's probably chewing because he's bored and has an overabundance of energy. So, here are a few things you can do: get a Chuck-it (http://www.amazon.com/Chuckit-Ball-Launcher-Colors-Vary/d...) and take him out to a park or field and let him fetch until he's totally exhausted, get a Walky Dog:( http://www.amazon.com/Walky-Hands-Free-Bicycle-Leash/dp/B...) and attach him to your bike and run that puppy until he's tired. Get him on a leash and rollerblade with him, go running with him. The first two options will be the easiest on you though and they are inexpensive. I don't think you can find the Walky Dog at Petco, but you can find the Chuck-it just about anywhere. You can also take him swimming at a local dog park.
We have a high-energy Golden Retriever and these are things that have worked for us. The Walky Dog is amazing as long as you are heavy enough on your bike that he can't pull you over. When our Golden was your dog's age, I used to clip him to the Walky Dog on my bike (he's 75 lbs, I'm 115) and he used to pull me for about a mile before he got tired. I wouldn't have to pedal once and he only pulled me off my bike once in the years that we did that. (and it was my fault that happened, so no fear. :))
Make sure you deplete your little guy of energy before you leave him for any stretch at the house alone. We also got a very heavy duty metal gate that he could not chew through to block him off from our living areas while we were gone. Those plastic and wood gates are worthless when you have a chewer who is motivated. We found our gate at Babies R Us and I think it was a Safety First gate. It was wide and tall and had only vertical bars so he couldn't climb it.
Hope this helps!
Hilary
P.S. Crating is fine. They're den animals, so they're quite comfortable in a crate. I just never liked leaving my dog in a crate for more than about 6 or 7 hours at a time. Just seems cruel.