Some PX-10s which were imported to the US in the 1970s were specified for standard 9/16" pedal threads. They were often (but not always) marked on the back of the crank arm "9/16 - 20
" along with the length of the arm in millimeters, such as "170". Even when un-marked, or even stamped "14x125
" (indicating French threads), they were often modified after purchase by local bike shops. You can test a standard pedal on the crank. If it is threaded for standard pedals it may actually fit, although perhaps tightly after all these years, so be sure to use a bit of grease on the threads. If they are French threads, it will be absolutely impossible to thread the pedal into the smaller hole more than perhaps a turn or two, so don't try to force it or you could ruin the cranks. Better to re-tap the threads.
The Stronglight cranks were very good quality and should clean and polish up very nicely with a bit of aluminum polish. The holes for the chainring bolts were drilled at diameter of 122 mm from the center axle - versus 130 for modern Shimano. This means the smallest possible chainrings available for the cranks were 38 tooth rings rather than 39 for Shimano, unfortunately
, this small size VERY difficult to find. The small chainring on your bike was probably 45 teeth - or possibly 42t, if you're lucky. This would tend to give the bike a higher "low" gears than is now common, so you may wish to find a freewheel with a 28 or 30 or 32 tooth sprocket for the largest inner cog to compensate.
One bit of good news for you: _ You will be pleased to hear that the 5 chainring bolts were the same size as those used on most modern crank sets. So, if yours are at all rusty or corroded you can easily replace the set of bolts for just a few dollars.
I happen to LOVE old French bikes, but I'll be the first to admit that there are many frustrating issues to deal with - such as basically ALL
of the threads on the bike. But, you really can work around this without much difficulty, so just proceed cautiously... and ask lots of questions on this forum.