OK, lets be Anoraks
10 for KLM (BUH,I,K,L,M,N,O,P,R,T)
2 for UTA (now Air France) BTDG,H
2 for JAL (8170,8176)
Old Fogey here can remember a photograph in Flight magazine at the time this work was being done, taken from above, of a (I think KLM) aircraft with a large oblong hole cut in the upper fuselage and the removed section laying alongside. And I seem to recall Boeing were doing the work themselves, but can't remember which plant was doing it.
Boeing presented this as a formal "program" (nowadays they would
PR it as a new aircraft model); the fact that they only did 14 shows it didn't really work out. If I recall correctly the cost of the rebuilding just wasn't justified by the additional revenue over the remaining service life of the aircraft (the oldest KLM one was already 10 years old when done).
The shipbuilding world, in contrast, are past masters at sawing through existing vessels, either horizontally or vertically, and inserting either whole new decks or lengthening the ship with a complete new section. Some ferries have had both done ! Aircraft seem to be a different matter.