Cut one coil from the 120Y coil and set aside. Trim around the bottom of the spring perch just above the weld.
Remove and set aside.
Grind the old weld smooth.
Re assemble and attach 2" split collars under the lower spring perch
You now have an increased spring rate that resists bottoming and an adjustable ride height. You will have to use the car's weight to compress the spring as you lift up under the lower spring perch with a hydraulic jack. Set the split collar and tighten. Don't worry they
each will hold over 2,700Kg that's like the weight of over 1 1/2 120ys. Do the other side and adjust till you have the ride height you want. I wouldn't drop more than the 60mm just to be safe.
You don't need to spend $1,200 on coil overs (or even $400) that you adjust once and never again. What's the sense of that??? I did mine including replacing the strut fluid for under $50 Canadian.
If you have the original struts you likely have the original dampers inside that sit in an oil bath and can be rebuilt. The oil is very watery and thin so I replaced with 20W motorcycle fork oil. Thicker oil is harder to push through the valving so the shock firms up nicely. Motorcycle fork oil comes in a variety of viscosities to suit your ride tastes.