Roof cracks

Lead can be removed with a propane torch, it melts at 621*F so that's not a big deal.

As far as repairing it, body filler won't cut it. Bondo will absorb water (its a seam after all), and it'll end up cracking in short order. Your best bet is to use lead again- after all, it lasted 40 years the first time.

The problem with that is there are fewer and fewer folks out there that are skilled in using lead to do bodywork. And of course, if its done wrong it will crack again. The body seam will have to be thoroughly cleaned, everything will have to be bare metal. That can be a problem because of the seam, I'd use a metal etch from a paint shop after everything was cleaned to get into the seam. Then it would need to be tinned, then leaded, then shaped with body file. Done right it should last another 40 years. Longer, if you do some chassis stiffening to reduce body flex at the seams.