Turns out there are two different springs. one. the shorter one for the double saddle post & rod:
Length 31″, 190 turns of 0.079″ diameter spring material, wound to 0.465″ inside diameter (0.620″ outside diameter).
The longer spring is for the single saddle post & rod:
Length 34″, 196 turns of 0.070″ diameter spring material, wound to 0.467 inside diameter (0.608″ outside diameter).
To be able to get the spring off the rod you need to be able to compress the spring a bit while removing the cotter pin at the end. I found a pice of 1/2″ PEX pipe (for residential water pipe use) handy as it has just the right inside diameter and enough wall thickness to push in the spring. Once you get the pin out and release the pressure on the spring, be ready to have the spring jump right into your face. When you do this, wear a set of leather work gloves to contain the spring force, letting them go more slowly.
Notice that on one end the springs have a little straight tail, that is the end near the saddle post (keeps the spring from turning).
It’ll be fun getting the springs back on…