The answer to your question will come if the springs can be compressed to the point where they bind - to the point where the coils are completely compressed with no space between them. If this occurs, you'll need different springs with a higher spring rate - fewer coils and more space between the coils.
That said, I don't think you'll have a problem. Have a look at the coils on my Dad's car. They are 400 pound rate springs. The number of coils and the space between them is similar to yours. I've never had a problem with the springs binding even though there's plenty of travel in the wheels.