Looks like a fun ride, good job on the conversion. I've been wanting to do a conversion myself.
Did you use something like this for the stem?
Also, BTW, /r/FixedGearBicycle is quite a bit more active than this sub.
The Peugeot has a Sugino RD2, new seat, new handlebars/wraps, new chain, Shimano Sora front brake, and flip flop rear hub (fixed gear/SS).
Only thing I'm gonna change right now is the pedals, probably something yellow to get some more color in there and have it pop. That, or I might get yellow wheels and white pedals?
Something like that maybe? IDk. I also need a head/rear light combo for the bike and we both need locks.
The Motobecane is pretty standard. Needs new grip tape and the rest is all pretty standard. Nothing to talk about really. We did switch the pedals already for the purple ones and got rid of the old strapped ones it had on it.
I hope you are okay.
Seeing that your bike isn't a multi-thousand dollar dream machine, you cannot go wrong with the Sunlite square taper bottom bracket. Its under $20, and the square taper will let you have many crankset choices.
A website listed this bottom bracket size for your bike, you may want to double check before ordering.
Edit: Since you are even asking this question, I recommend that you take the bike to a shop. You probably do not have the necessary tools.