Having read through the thread posts, converting the Aifix Sunderland, the bow section
and rear turret section will be your biggest issue, depending on whether you build your
Sandringham as one with the turrets faired over, or a total conversion, where the entire
bow and rear section were rebuilt.
Addition of 'Liner" type windows as opposed to portholes (they did retain some portholes).
The WEM set (interior) won't suit you here, as Sunderlands turned Sandringham,
had the flight deck quite different to the military Sunderland. if you can find photos of
Kermit Weeks Sandringham/Sunderland you should get some ideas.
From the photos I have seen, it appears that the Aerolineas Argintinas were previously
Mk V Sunderlands, so will have the R 1830 Pratt & Whitney engines, as opposed to
the Bristol Pegasus Mk XvII's . Note the Cowling will be different also as will exhausts
(fish tail type).
Good luck in your build
Regards
Alan