Not to throw you off....but...You know the GM coil spring special tool was a big threaded rod and washer that went through the bottom shock hole and it was then threaded into a shoe shaped plate that slid in between the spring coils. It held the coil on the lower arm.
So.....A common flat rate practice was to reverse the operation to feed the threaded rod down through the upper shock hole and hold the coil spring up into the frame pocket with the shoe so you can easily remove and replace the lower control arm. You can also use it to trim the lower coils.
If you know any GM techs they should have it.
Snap on has a similar tool.
Please don't risk your safety by using a cheap $30 unit.