The best way to get that effect would be to paint over a car that was screen or pad printed in the original scheme you want to paint over. The reason the previous scheme would be visible is that the original lettering would be a different layer or level of paint and it would show up as a "shadow" under the new paint. A decal would not show the individual lettering unless each letter was applied separately, it would just show the shape of the entire piece of decal film.
Bill in FtL
