https://imgur.com/a/uJ2oI9f link assist.
Mont Cenis is not far from being one of the best frames you can get in the mid-80s from Peugeot, the Super Vitus tubing (making it a PSV-10 or PSN-10 if I recall) is, per my recollection, even lighter than the Reynolds 531 frames, although the lack of seat pinch bolt meant you're stuck using a quill seat post, and those often got stuck.
Value as-is? Assuming no rust and no dents/dings and no mechanical issues, just the frame/fork/stem/seatpost/crankset is worth $100-150 on a quick sale to the right buyer, but could fetch up to $200-250 if you sit on it for a while for someone like me who'd really love to have one. But the real put-off for most people will be the current state, stripped of its nearly $150-200 in drivetrain parts and another $150 in wheelset and brakes you'd need to replace to get this back to stock.
Sucks you're not closer, that's my side and or I'd snap that up from you in a heartbeat! It's sad to see something so high up in Peugeot's food chain scraped of all parts and relegated to the life of a fixed-gear frankenbike.
If you get me the serial number of the bottom bracket shell (under the bike) I can get you the exact year and we may be able to nail down the exact model. I suspect the serial will start with "Y4" or "Y5" possibly "B4" or "B5" but the 32nd digit may be a 6. It's mid-80s for sure.