It would require a deep-hole drill jig bolted to the block similar to what's used to make a gun barrel. The process could be done on a big lathe with a long bed, with the drill bit turned by the headstock, and the block set up very precisely on the carriage. The setup time and labor cost would far exceed the cost of purchasing a factory-drilled block, as long as they are available. Just because it's possible to do something doesn't mean it's a good idea if other methods of getting the same thing accomplished are possible.
Jerry
