Felts were pre-cut in French made packs. Don't know the carpets but a deal was done with NZ for tariff write off in return for rear mufflers and carpets. Probably applied with the 504. (Just quietly and don't tell the Kiwis but the mufflers were crap).
Odd to say there may still be new materials out there. Whenever a change of material happened the old packs would be thrown out and were free for people to take. I've still got packs of pre-cut lining material for 1973 model R12 wagons! There's lots of old factory stuff about that never gets advertised and just ends up in a tip. All the body assembly jigs for the 403 and 404 and R10 were stored at Georgian Engineering but would have been scrapped long ago.