Rusted nuts can be a real pain. If you cant get then to move, a good way I have found is a strong pair of locking grips (mole / vice grips) and plenty of hot water. Pour the hot water slowly over the nut (if possible); this will causethe metal to expand and may slacken it enough for you to get it off.
Obviously this method is less useful for nuts that are underneath something so you cant pour water on it, but there are other ways of warming up the metal......
Some WD40 on the nuts 10 mins before you start, a breaker bar and those nuts won't be a problem.
If you attempt to just use a rachet only you will struggle. I have a 4 foot breaker bar that can easily be used on the suspension nuts and makes it simple.