I had to do this again recently on my '68, and I will tell you there is NOTHING I hate more than messing with coil springs, front or rear. Here is what I did.
First, as others have said, getting the car as far off the ground as possible so you can drop the axle way down after shocks, panhard bar, upper control arms, driveshaft, etc. are all disconnected is key.
I placed the springs in the pockets in the frame and used a heavy duty ratchet strap over the frame to hold the springs firmly in place, NOT compress them. Then I used my coil spring compressors on the front of the springs (on either side of the lower control arms) to compress them on one side - if you've ever looked at them installed you know they are not straight, but are curved since the lower control arms are not parallel with the top surface of the frame pockets.
The curve in the springs allowed me to then use a floor jack to lift the axle up, place the spring cups in the bottom of the springs, align the holes between the spring cups and lower control arms, and then run the fasteners through the holes. It was then just a matter of alternating between lifting the axle up with the floor jack and torqueing the fasteners to secure the springs to the lower control arms.
Sorry for the long description. This worked for me and was the least amount of trouble I've had putting them in. I still cursed PLENTY and was amazed at how high I got a wrench to bounce off a concrete floor.
1968 Impala SS