Well I'm not totally sure it was released in 79. On Imdb there is no Italian release date which is not surprising, in 71 Lucas was totally unknown (American Graffiti wasn't such a hit here) and THX is quite a "niche" film, I doubt it would have been released in 1971 (my guess is that we had to wait at least till 1977).

Laserdiscs weren't extremely popular here and VHS were yet to come so my guess is that this film only went on TV (or at most in very few local cinemas). Unfortunately it's really hard to find any information, there is practically no data available online for most of the films of those years.

I wouldn't even be surprised if the film become available for the first time only on VHS in the late 80s/early90s

Again on the "unknown-ness" (allow me to invent a word) of Georgy-boy:

I don't know if this is from a VHS or a cinema poster (looks like a VHS cover to me) but you can notice that Francis Ford Coppola is the main name up there, director George Lucas was left as a bottom note.

By the way, do you have this poster in English? Looks like a typical Italian way of attracting more audiance (I'm referring to the boob)