500,
The rates that normally come with AVOs are 350lb front and 200lb rear. It is the rears that are excessively hard. Try 175lb on the rear, but first turn all the dampers to the softest settings and then work up five clicks at a time. When you get close to what you feel is comfortable, then you can fine tune 1/2 clicks at a time.

Ryan,
Until you determine the weight of the car, then you can't say what springs would be a starting point. What might be good for a car with full interior, would be too hard for a stripped out car. The lighter the car, the lower the spring rates can be to achieve the same thing.