I gave up saving old spokes. I used to have all these little bundles of spokes waiting decades for the right combination of hub and rim to build.

Dan's Comp will cut and thread exactly the right length spokes that you need in the exact quantity that you need. They're cheap too. Living near St Louis, I will typically receive a spoke order in 3 days, sometimes only 2. They do require that you place a spoke order by telephone rather than on line.

If cross 4 lacing overlaps the heads of the adjoining spoke at the hub, think of what's happening at the angle where the spoke enters the rim.