67 Mustang-6

Yeah I know its a six,but gotta love them. I just got this car and my son and I plan on doing a restore for him(it was his grandfathers car),what I need to know is what is how much water this holds so we can drain it and put in new antifreeze for the winter,it is a 6 and not worth much to some but to him it is,so any help would be appericated. As you can tell we are new to this.