The factory stem shifters were a blessedly short-lived experiment, introduced late in 1972 and terminated by 1974. I worked at a Peugeot dealership during that period, and those things were indeed dreadful.
If your UO-8 came from the factory with downtube shifters, it will have a single drive side shifter boss -- that way, the French could make 5- and 10-speed frames using the same setup. For a 10-speed, Simplex made a clamp-on left side shift lever boss. My current UO-8 fits this category -- I chiseled off the right side Simplex-specific boss and covered the area with a SunTour double cable stop to accommodate SunTour stem shifters for my wife, later SunTour barcons for me.
If your UO-8 came with stem shifters, it will have -- as others have noted -- dual cable stops, which are ideal for barcons and various brake lever mounted shifting systems.
I have always viewed stem shifters the way I view a column-mounted automotive shifter. They seem convenient for the casual user, but the enthusiast always wanted the shorter, more positive linkage provided by downtube shifters or a floor-mounted gearshift.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069