Oh well; ANYWAYS
I used to have that exact same frame as my commuter; let me guess, from the decals and the HLE (manganese steel) sticker and the down tube shifters; that is a corbier model.
Just try to keep it out of the rain and wipe it down whenever you ride it after/ in the rain.
Also try not to skid that much with it as the seat stays of peugeots of that period are not that strong and will become unbrazed (I found this out the hard way and repaired the frame for much more than it is worth for sentimental value)
Don't believe me? I can tell you that the frame flexes a lot, just apply some pressure to the crankset from one side and the entire bike frame will flex.
As for the chainline, you should be able to keep the same BB and crank, just use the outer ring/ part of the crank to mount a chainring; and your chainline should be very straight with a traditional 120mm track hub.