Oh those "plugs" are easy...I put radiator petcocks on both sides so i can drain it if need be...forgot about those...i'll crack loose those with some super penetrant before starting the job then let those drain first before dumping the block. I have a 5HP Karcher Gas Powered Pressure Washer. I can hook that up before the compressed so I can get everything out. I was going to pull the heater core hoses and slip one into a bucket and feed some tap water (low pressure) to get the dirty crud out of there too.