It’s relatively simple to do: just get a rip of the English version, say the laserdisc, along with it’s high quality audio, and load it on your timeline. Resize the ld video so it only takes up a corner. Then import just the video of the Italian print and cut and paste the shots so both images are in sync. Erase the video of the ld and then export. Voila.

For this particular project, you’d need to also find a different source for the titles and the Buck Rodgers serial at the beginning.