On a '62 MGB that I worked on several years ago (its # was 938, earliest one I ever saw), I rebuilt that area using some sheetmetal, trimmed to fit. I had to do some shaping, as I recall, for the recesses, but it wasn't difficult to repair.
If you do repair the existing panel, drill a small hole (1/8" is typical) at the end of each and every crack to eliminate the stress risers, otherwise the cracks can continue to grow after the welding reapairs.
If you were a bit closer, I'd offer to do it for you /bcforum/images/%%GRAEMLIN_URL%%/wink.gif