Use some PB blaster penetrating oil first before you try to loosen them up. Other wise you will spin the cage nut.

I put hotchkiss 1" lowering springs in my '69. The fronts are amazing, great ride and handles ok with the stance I wanted. The rears however were to soft and the back end sagged. And it was worse with extra load. I added air bags and that helped a lot.

This was mine with 1 1/2" lowering springs in the front......and then with 2" lowering springs on the rear.