You'll want to use lead as it will outlast any filler + it will expand and contract better than filler so you don't end up with lines in your paint, which will happen as I have seen it.

Lead work is something you may have to do yourself depending on who your painter guy is. Any sort of modern collision repair body shop won't touch the stuff. Guys that do insurance work will reject the idea because they have no idea how to do it and have no need for that skill in a world of bondo sculpting.

Local body supply shops don't even sell autobody dollys any more. They rough the damaged areas back into the general shape with hammers and pullers and cover it with bondo and then spend hours sanding it all back off.