Yes and No.. up to early 72 they did.. mid year 72 and 73 they had the boss for the drain hole in the block, but it was not drilled. 74 and later don't have the boss even. But I always add them in a rebuild, either drill the boss if it has one, or just the side of the block.. be careful doing that, as you have to put it in the correct location, so do it with the frost plugs out, and make sure there is room behind the hole so the 1/8 pipe tap can go thru, and make the threads for the plug your going to install. The cylinder walls get real close to the outside of the block in places, so don't guess. The only exception to that would be a concours rebuild, but don't do too many of those on the later blocks.
You could install a radiator petcock instead of a pipe plug. Makes draining the block a little easier.
