Not sure what the bike originally came with, but I'd suggest the following to come up with a good, early 80's, all French, period correct Peugeot Super Comp build:
(BTW, all the Campagnolo, and I think, Shimano and Modolo stuff were most likely later add-ons).
The Stronglight 105bis crankset on the bike could be original.. It is a very desirable, period correct, crankset and you should really keep it on the bike.
Brakeset could have been Mafac/Spidel LA sidepulls.
The pedals, Maillard 700 quills.
Saddle, Ideale 1000 or 2000, but a Brooks Pro with large rivets will look spectacular on this bike too!
Seapost, a Simplex fluted aluminum post.
Stem, an Atax/Peugeot quill stem.
Handlebar, A Philippe Tour de France model bar.
Bennoto Cello handlebar tape, usually in white.
Derailleurs, SLJ5500.
Shifters, first series Simplex retrofrictions (which I think you already have on the bike).
Hubs, 36H Maillard 700 low flange.
Rims, 36H Mavic Monthlery Pro tubular rims.
Spokes, DT stainless steel, straight guage or dubmle butted.
Tires, Wolber (if you can still find good ones) or Hutchinson tubular tires.
Freewheel, Maillard 700 compact 6 speeds.
Chain Sedisport silver.
Toe clips, Christophe Aluminum.
Straps, Christophe Plus.
Headset, Stronglight P series chromed steel, but you can also go to a much lighter Stronglight A9.
BB, Stronglight loose ball with chromed steel cupset and 118mm spindle length to work with most Stronglight double cranks from that era. You can try to find a Bador BB with aluminum cups and cartridge bearings, but those are close to unobtanium these days.

Some of these items might be different and higher in quality than what was originally on the bike, when the first owner bopught it, but they will surely enhance the bike to surely be a top level Peugeot from the early 80's.