You’re talking about pan/scan and tilt/scan. Letterboxing is adding borders on the top and bottom; pillarboxing is adding borders on the sides.
Of course that’s what letterboxing and pillarboxing are. The footage that we have in 4:3 has already been panned and scanned. I am indeed talking about letterboxing and pillarboxing it to integrate it with widescreen footage (without cropping either). Just look at the picture above!