As a suggestion, when you have the engine apart, Inspect for main cap fretting. That is when metal transfers from the block to the cap. It looks like little craters in the cap or block where the two pieces come together. Fretting is a result of the cap moving on the block due to detonation. Have the block magnafluxed in the main cap area. Cracks will develop in the bolt hole areas that may not be visible without magnaflux. The engine in the picture was running when it was disassembled. It had 6 bent rods!!!! If this block had been reused, it would have been a timebomb.
Your block is already drilled and tapped with coolant drain plugs on each back. Look at the side of the block just above where the dipstick enters. You'll see a brass colored square plug. There is another one on the other side. Pull those out and you'll drain all the coolant out of the block.
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