Yeah, what Merk said.
If it's a regular coil spring, with the shock absorber going through the center, you have two choices, both very similar in design.
The first has two sets of fingers with a threaded rod going through them. The fingers get installed through the shock mount into the center of the spring and worked into place.
The second has one set of fingers for the top of the spring (inside), and a plate at the bottom that goes through the bottom part of the spring.
You seen to get a little more purchase with the two-finger style, particularly if the control arms are contoured in such a way that they'd impede the plate going through the spring.
What I've found to be of the utmost importance is the type of threads on the rod that draws the spring down. I have one that's got fine threads, and another with square Acme threads. The square threads are much better--they do their work easier and faster than the fine threads. My Acme thread compressor is from KD tools, and I bought it even though my fine-thread Mac compressor was fine.
Now, I will tell you another thing I've found on every vehicle I've used these on: The threaded shaft always ends up going too high into the spring pocket and bottoming out before the spring is compressed. This is the case with first generation Camaros, 2nd Gen Novas, Tri-5 Chevys, Dodge Dakotas, and '54 Buicks.
The fix is to take a 6-inch long piece of black pipe and put it between the nut on the shaft, and the bottom set of fingers (or plate). You'll take up the excess 6-inches of threaded rod on the bottom, rather than run it through the top set of fingers before you start compression.
I bought a piece of pipe and a couple big washers and made them a permanent part of the compressor.
-Brad
