Master cylinder

I'm not sure if it was a production change, or a supplier substitution in the replacement parts chain. But the units you get now are frequently not drilled, regardless of what year they are listed for. I drilled and tapped my last one, too. I have never seen any documentation on this feature, but it probably wouldn't be accurate, anyway. The parts listings for A-body master cylinders are already a mess. Because all the different MCs used from 67 through 76 are direct bolt-in replacements, it seems like the supply houses haven't bothered to keep track of the details -- it fits, so who cares about bore diameter or piston retainers?