Thank you, especially for that lead on the paint. It's not common to find close modern matches to some of these older colors. I'll obtain a bottle of that post haste.
I've had a Motobecane before with Swiss threads. I'd be happy if these are -- that eliminates the issue of undoing the drive side cup while pedaling. Filing this in the if-it's-not-patently-broke-then-don't-fix-it category, I have not removed the crank arms. I took the rings off and they (and the arms) cleaned up really nice with some baby wipes (my favorite bike cleaning tools!). But the cranks spin smooth with no apparent issues, so I'm going to leave them be for now. I've had problems with French-threaded cups before, and with square taper cranks creaking after a reinstall before...Swiss threads would fix the unthreading of French cups, but I plan to leave the cranks be unless I really need to remove them to avoid any unfortunate noise. If the system makes noise after I reassemble everything...well, I guess I'll cross that bridge then.
Interestingly, your '83 model has a B + 7 numbers. My presumably '81 model has a B + 8 numbers. Yours is 3 04 + serial number 6985. Mine is 1 02 + serial number 48441. I know the numbering on these Peugeots is inconsistent at best. Maybe different models or frame materials (PBN10, PX10; or Carbolite 103 vs Vitus 181 vs Reynolds, etc.) had different serial number formats. Perhaps they figured they'd build more of the less expensive models.
The front rim is definitely a MAVIC (unless someone put the red-diamond sticker on another rim!). Both rims seem to have the same profile -- the exterior width of both is exactly 20.0mm. That Moto I previously owned had aluminum Rigida 622s, and these do not appear to be the same as those. These do have eyelets and are 36h rims.
Front and rear rims, respectively:
