Relocation of Rear Springs 67 Dart

Looking for information on relocating my rear springs to make room for wider wheels/tires.
I put wheels on with 4.5 inch back set and 255/60/15 tires. The tires hit the springs so I installed a 1/4 inch wheel spacer. My opinion, the tire still doesn't have enough clearance...about 1/8 inch from spring.
Does anyone have information on steps to install the offset spring hangers?