I didn't see it posted yet, so I'll add this:
The excess drain hole sizes are
1x 1/2", located in the front, passenger side corner of the block.
2x 11/16", located on the front edge of the block.
2x 5/8", located on the rear edge of the block.
Even though midship is dick, he does have the holes filled in the best way possible in the picture he added. Tapping the block and using threaded plugs is the way to go. I'm using water plugs and tapping them in, which will work fine because there is little pressure (only blow by) coming through those passages. I would use threaded plugs but my engine is assembled and I don't want to risk metal shavings contaminating the engine. If you're at the bare block stage, thread the holes. Might as well
