It depends on how extensive your planning on going in your project. If your are doing a rebuild and while the valves are being done they also reface the rocker arm tips it shouldn't matter if they are mixed up.

If your just taking it apart to clean and inspect, the rockers should be kept with the valves they have run on and set up unique wear patterns with. The springs really don't care where they go as their main function is just to keep side pressure on the rocker to help it aligned with the valve tip.

The real big thing on these (and any other old rocker shaft engine) is to make sure the INSIDE of the rocker shaft is completly cleaned, which entails the removal of the end plugs.