There are companys that make radios that fit in the dash, there are companys that convert originals with new guts. ie FM parts in an AM, but nobody repops originals, finding an original AM to fit in your car should not be a problem.
AM radios in good working order are for sale in places like ebay all the time. Place an ad on Team Chevelle, lots of options, and they are reasonable priced mostly.
There are several folks that restore original GM/Delco radios. I used Tony Mac also known as the "Wonderbar Man" to restore my AM/FM. You can pick up non-working radios for as little as $35 bucks and as high as $300. Check out the radio tech section on this site for some useful info on model year radios.
You can also look on Ebay under "Ebay Motors". Type in "1967 chevlle radio", or "67 Chevrolet radio", etc. and you may find some listings. Some are in pretty good shape, and you don't have to leave your house to look.
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