A friend has a .45 1911 that was custom made into a competition race gun. The bushing is not standard, but is a screw-in type, so it doesn't disassemble like the Govt. Model does.
How easy, or hard, is it to convert it back to its original configuration so its easier to disassemble and reassemble?
Sounds about right. Most 1911 models are fairly standard. Even ones that have been tweaked. Should simply be a question of just replacing the relevant parts.
The only way that would not be the case is if someone took a Grinder or Dremel to the Frame and or slide. As that can affect how parts fit and tolerances. Depending on how much they took off of either. Every once in a while you get a company that makes a proprietary tweak to whatever model they’re pedaling. Though that’s not all that common a practice on some of the widely produced things like 1911s. As that’s a good way to piss off your prospective market l.
From your question and the sounds of it though. It sounds more like someone just played around mix and match with the parts. Which is generally more typical.