TheJoe: So the original game is contained in the tenta.cle file.
bgbennyboy is working on updating Double Fine Explorer to properly support extracting from it, but until then:
https://quickandeasysoftware.net/software/monkey-island-explorer The Monkey Island Explorer actually works well enough to extract the original game files. Select Monkey Island 1 mode, show "all files" and open tenta.cle. Filter by .000, .001 and .sou files, extract those by clicking "save files" and load them in ScummVM as normal.
Maniac Mansion is included there as well - those are all the *.lfl files in the maniac/ folder but having fun extracting those since you can only do it one file at a time. If you try to "Save all files" it'll crash on the first texture it tries to extract.
Doublefine Explorer will hopefully get updated within the next day or two. I also do not know if the original game data files are modified in any way - I do not have the original game to compare them to.
Have fun.
Edit: ScummVM did not warn me about modified files on launch, so I'm gonna guess they're the original files.
You wouldn't happen to know which extracted files from Monkey Island 1 & 2 Special Edition SCUMMVM requires would you?