Spring rates and wheel (spring) rates are different. Wheel rate takes into account the suspension geometry. The length of the A-arm from the inner mounts to the shock mount, the length from the shock mount to the tire contact patch and the inclination of the shock along with the spring rate gives you the wheel rate. There are wheel rate calculators on the internet. Spring rates are determined by vehicle weight, suspension geometry and dynamic and areo loads. Shocks control everything. Shocks are a lengthy topic for another day.
For our race cars shock tuning was 75% to 80% of suspension adjustments.
Ideally you do not want that gap. I have not done the math for stock Pantera A-arms and wheel widths but 400 pounds seems a little high. zr1 is correct in saying your shocks are probably too long. Keep in mind that you can get 400 Lb springs that are 10 inches long and 400 Lb springs that are 14 inches long and practically any other length. I suspect your spring/shock package is not correct for the car.
Unless EVERYTHING is stock you must first establish the ride height that you want to live with and work from there. Them measure the distance from shock mount to mount. Then do all the math for the correct spring rate. Then determine the max bump and droop to determine the shock length. Then get the shocks valved accordingly. That will get you in the ball park
OR
Call zr1 for the correct spring/shock package.
Just my 2 cents