[19Fordy]

If you do a search for SPRING SPREADER lots of good ideas appear.
Measure the distance between your rear spring eyes. Then you can make your own spreader. I think this home made spreader is about 38-39 in. so it will fit between the spring eyes. Then you can "turn it outward" to spread the spring. You only need to spread the spring eyes outward a small amount to release the tension. Can also be used on front spring. This is a 40 Ford with stock rear spring.
Porta Power is and easiest way to go if you have one.