Let me give you my .02 cents. Tack weld new panels just enough to keep them in place and provide some structural support. The reason for this, is it makes it easier to reposition the panel if you later find that the fit of the adjacent panel doesn't match up, such as cowl-to-door, door to cab corner, etc.
Carl


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