You're not going to get a lot of optical vignetting (cos^4 falloff) from a 120 mm lens on 4x5. You'll probably get substantial image degradation towards the corners with a lens around 120 mm made for a 6x6 or 6x7 camera.

Your best best at 4-5 feet would be a shorter lens made for a 6x6 camera. And it won't give you exactly what you want.