I have come across some of these heaters too. They were for LHD Cars, but some were fitted in to our late Mokes. Some of the heater cases have holes in both sides, so you can remove the core and fit it out the correct side. The ones that don't, I re-drill them (16 mm hole saw).
Then you'll need way less hose, it won't kink up and you won't think you'be being over-run by a serpent every time you look down.
I know Adrad make cores for these, but they do not sell direct, so find a Radiator Repairer (coff, coff) who sources from Adrad.
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