See if you can fish a torch in there to add some heat. A small acetylene torch used for soldering would probably be doable. This torch only has a small acetylene tank (no oxygen) and a small hand piece on a hose.
I don't think there is room for a propane torch.
A buddy of mine just bit the bullet and cut an access hole through the inner door panel with a 1/16" cutoff wheel. Doing a neat job will allow you to easily weld the cutout metal right back in place.
Carl


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission