The scenes were removed by US distributors and thus never dubbed into English during the dub session in 65/66. The first release of them in nay territory besides Italy that I know of is the MGM 1998 LD and DVD. For the Rome premiere version these were all present plus the grotto scene (which I despise for some reason) and the Socorro sequence. The latter two were removed from the general Italian release, which is why the entire extended version has the full Italian mono for 180 minutes.

I don't know if any video releases would have them already in the cut. It should be pretty easy to sync the English mono PCM to the Mondo release (which BTW looks stunning to my eyes in screencaps, can't wait to get one for myself it looks much more like the film should.) Either simply add in the English and leave the other scenes in the italian PCM on the disc, or if necessary track down the 98 LD and add in that PCM from the deleted scenes.