Once you go spring over, very few components are still stock and no two will be the same, so, in order to get your monies worth, no there is no average length that will work. Grab a tape, a beer, and a buddy and stretch it out after you get the springs on. A forklift works good for this, otherwise a loading dock wall will do. A quick search here will bring up all you need on this and most any other subject.
Good luck and welcome.
If it wasn't done the hard way, I didn't do it.