I also have a Superlux, got it with the mafac racer brakes, the original fork, but it had this crazy high end bottom bracket, I've been looking for specifications on it as well, G Lapierre is really hard to find stuff about.
But my Superlux had a super ****ed paintjob, so I'm in the middle of refinishing it (just spray paint and clear coat for now, I'll have it powdercoated to factory og one day) and I found that the braising was really messily done.
All in all, though, I ADORE this bicycle. Can't wait to find out more info.
^Yes they were messily braised 'cause they were a $100 bike. Pretty complicated brazing with a mixte. It's amazing they could make any money selling those bikes. Multi-color, flamboyant paint, pin-striping, and ten speed gearing to boot.