A step is missing:

REMOVE THERMOSTAT.

 

You should have the car sitting level or slightly nose down {by jacking up the rear end} when draining the cooling system. Think about how you dump a bucket, you make the bottom higher than the top so the water can drain out by gravity.

Jack the front passengers side up or maybe drive it up on ramps, if you have them, when filling it.

You want the front end or at least the passengers side higher so the heater core will fill with coolant instead of air.

 

And what Donbrew stated, remove the T-stat! During draining yes have the front end down, then with the new T-stat installed jack up the front right corner just six inches or so the rad hose cap is the highest point, ensure the rad drain pet**** is closed, then fill the rad with 50/50 Dexcool! Turn the heater on to full heat and run till it comes up to temperature, check the coolant level ! It should take 1 to 2 gallons

 

I couldn't stop laughing long enough to type in what the previous three wrote!!

 

Ah grasshopper front end down for drain rad, up for fill rad! Well golly Sargent Carter !

 

The cooling system takes just short of 2 gallons (including the overflow tank).