Many Q's Aaron. Campy seat post? stamped 27? yes and yes
I wasn't sure for mine as it had a stove pipe in it. Got a 27.2 and it fit. My 531 decal says 3 main tubes, FWIWI don't see a tubing sticker

Are those Balilla brakes? Interesting. Mine came with Uni 61's yes - believe original

Is the triple crank 144 BCD? 151? Did they have triple record cranks back then? 151! Probably not original...these are the real triples, not the tripleized double

I dig the 3TTT bar and stem. Could be original, as I think Avenia and others built these up from frames. This did come through Avenia

What kind of rims? No Record hubs? Fiamme red/no record high flange

Oil nipple on the BB as well? yes

And, lastly, surprised the owner got what looks like a Campy seat post binder bolt to hold on that QR brake bracket. sugino

Super cool bike. I like the colors.
Thanks!!