On p.97 of the book Skywalking (first printing), it is stated that 4 minutes of material were cut out of Lucas' version for the 1971 theatrical cut (but later restored), which were mainly to do with the White Limbo sequence and George's bizarre attempts at humour. So, this gives us some clue as to what was added for the re-release in the late 70s that subsequently became the standard pre-SE home video version. However, it also says "mainly", not exclusively, so there might have been other bits taken out. But at least if this Italian version is missing some parts from the limbo and some of the weird "humour", we can at least say that this probably reflects the original American editing.