Lower door patch repair

I have a nice 72 demon door which unfortunately is rusted along the lower inside edge where the pinch weld is. I was thinking about cutting off the lower door panel and installing a new lower door patch panel, however, it would require that I also add some sheetmetal to the inside of the door where it actually goes into the pich weld, as this is what is rotted. Has anyboy attempted this with success or should I be looking for a good used door for the car? Thanks