First- - - -be sure the whole engine, not just the radiator gets drained. The position of the water pump inlet on a stovebolt allows a lot of coolant (water) to stay trapped in the block. The block drain is down low on the water jacket at the driver's side rear, and sometimes it takes a bit of poking and prodding of the crud in the block to get it to flow.

Once the block is empty, refill the cooling system with a 50:50 mix of antifreeze and water. That mix is good to -37 degrees F. If you're lazy and want to pay antifreeze prices for water, 50:50 pre-mixed coolant is available. If it gets colder than that here in Tennessee, I'm moving to Tahiti!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!