As Djordje suggests, you should be able to open them, change the subtype and resave (with a new name). I don't recall trying it with lamps but it works with doors, windows, labels, markers, etc. so I assume it is the same.
There may be problems in the scripts though. Changing the subtype may strip out some parameters and cause errors. If so these would likely only be in the 3D script so if that isn't needed the code could be deleted.
