The conversion kit I was looking at some time ago had a modified lip with the new barrel for proper feed of the 9mil ammo, so that with the slide, spring, and of course mag change were all that was required.
The problem with the .45 model is the ejector is in a different place and even if you could find a barrel and slide to git the 1911, the ejector would hot allow the slide to be mounted.
The barrels on different models are not the same. They are of different lengths and even different configurations on some of the short models. Full length 5” barrels are extremely common. I have no idea about the officers model but am sure it would be less common than the regular barrel.