Well, in terms of possible coachbuilders, let's see here...
In the early 1950's, Vignale was big into egg crate grilles.
During the same timeframe, both Ghia and Pininfarina produced models with quad headlights with similar front end proportioning as this car - Pininfarina with the Alfa 6C 2500 "Coupe Speciale" and previously mentioned, Ghia's Cadillac.
On the other hand, the workmanship of this car doesn't look very good.
The front bumper looks pretty crude and definitely isn't an original to the XK120. The windshield bar is removed, but the wiper arm location is changed from the XK and doesn't look very effective.
I'm going to stick with an Italian coachbuilder though.