looks like an '86 with that chrome treatment. You have a handle on the #'s. You felt the ridges, the rifling I suppose. Gara frames, Euro ones, Sport models not imported much in the US. got that Chrome treatment; only for a couple of years SLX Corsa Stradas did.
It's not 753, not with all that's been observed by you, not with that rear triangle.
A GREAT FIND !