Now, I'm thinking your talking about the cooling system and not the interior, couple ways that I know,
Pull radiator, pull thermostat, jack up the back of the car as high as you can, I'd pop out the front two freeze plugs if you can.
Pull engine.
Someone may have a better idea.
Flush it through the heater hoses.
Disconnect one hose-hook a garden hose to it-take off the rad cap and let it over flow into a pan until it's just water. Then switch heater hoses and do it again. Put the cap back on. With one heater hose off,install another section of hose onto the heater core or block(depending on where you take it off from lol.) and shoot air (regulate to 10lbs)through it to push all the water out of the system and through the added on extra hose into a pan.
I use a flush gun -which allows me to use water and air together-or separate ,but I've also done the garden hose and air nozzle tons of times and has always worked well for me lol