Create some reference geometry sketch and dimension it's entities.
Usually a helix is generated from a 2D sketch of a circle. You can grab that.
Otherwise, you can make sketches based on the solid geometry.
Download the correct SW CAD file from McMaster-Carr each time you need one.
The best part of McMaster files are the Equation Table included with each spring.
RMB on Equations in the Tree and select Manage Equations.
Doing this I directly edit the overall length to accurately reflect the compressed length in my assemblies. Works like a charm.