Mandoble, as far as i know in the LW planes were most often not converted.
There are examples of A8 frames used to build D9 or old style canopies, but i think (beside prototypes) new planes were never converted from planes that already flew on the front.
Unlike the RAF, were whole squads were converted, the LW delivered factory new planes to the squads, even when there were just minor changes.
And those minor changes also cause a change in the werknummern.