More than likely, if Saint Sheldon made it rideable, then there's probably not too much wrong with it now. The "French bits" with peculiar metric threading that give people trouble when refurbishing those bikes are: bottom bracket assembly, pedals, stem, rear derailleur hanger, and if the rear wheel was built around a French hub, then the freewheel -- they're all "French threaded" or some other arcane standard. Of these, the last is perhaps the most aggravating, in my opinion. I don't know where Peugeot was in 1968-1971 regarding the crankset for a PX-10 -- during that time a lot of cycling was still changing from cottered (affects both bottom bracket and crankset) to square tapered. If your crank does not obviously have cotter pins holding the cranks to the bottom bracket, then you'll be fine. Unlike in 2004, there are enough people interested in French-threaded bikes that you can buy replacement sealed cartridge-bearing bottom brackets with French cups (the screw-on bits); they're very reasonably priced. Pedals: can always use ISO/English ones having 9/16-20 threads simply by having the (existing) cranks rethreaded from the French 14 x 1.25 mm. Stems are easy to fix: just carefully sand an ISO 22.2 mm stem column down to 22.0 mm. It's not too difficult to find French diameter seatposts, really, though because they're typically incrementally smaller than what's current, that cannot be "adapted". But it's probably not going to be necessary to invest in a new seatpost unless the current one was trashed for some reason. With regard to the rear derailleur hanger: if it's integral (rather than a separate screwed-on hanger), then you pretty much have to use one of a few different specific models, and the black delrin in the Simplex Prestige models is notorious for breaking after years of use, like the front derailleur pictured above. These integral hangers can be adapted to ISO "Campagnolo standard", permitting a wide variety of derailleur choices, but purists frown on that, and doing so takes a certain knack.
I recommend posting enough times on this forum (ten) so that you can upload photos, and then take some overall and detail shots. People here will ask if they want to see something special photographed once they see the overall picture. Then you'll get some very informed advice on what to do with what. And, you would be surprised how generous Bike Forum folk are with both assistance and materials to get you to the right place, and save another PX-10.
Last edited by Charles Wahl; 08-01-20 at 06:18 PM.