When i lowered my 1200, i found some springs from a 210 from the junkyard and cut those. The wire size of the spring was a little bigger/ stiffer. I started by measuring the car height, cutting off a half coil ,reinstalling the struts and taking another measurment. You should have a pretty good idea of how much each half coil taken off will lower the car.
It's doen't take too long to partially reassemble the car to measure since you don't have to assemble the brake lines, swaybar and strut rods.
I think you'll have to do more than just cut/replace springs to lower your car 3". I think you'll run out of suspension travel, even with the bumpstops removed.