What is a sill panel? Inner cowl panel?
If so, then what you are dealing with is an area where the flange of the floor panel, the rocker panel, and the bottom edge of the inner cowl panel are layered together. They are welded all together at different stages of the build. This makes it a challenge for restoration of this area without removing each of these 3 panels.

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