73' B3 340 Duster pro touring build

Okay the front springs are 350 and are 8 1/2" at ride height on a 10" spring. The rear are 9 3/8" ride height on a 12" spring. Any guess on what to try for spring rate
next ??

It is in the adjustable range now (with pre-load adjustment) to get your stance dialed in...... I would wait until car the is done and ALL weight (including fluids) is on the car....then make a the decision. You might be surprised how adding your hood will change (lower) the ride height and that % measurement will change.