Yep, the pipe plugs will yield nothing in an old block unless the guy has removed them before and dislodged the cement behind them. You can with a screwdriver but dont hammer it in, just poke and turn to root the sediment out and be prepared for a jet of nasty coolant to follow it! I took about a pound of crap out of a 64 273 block when I took all the core plugs out, especially the 2 in the trans flange, and a few core wires.
