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Thank you for posting this cycle.
Hubs look more like NEWSTAR than Juy (Simplex).
Date right near 1971. This was about the last year for this model of Simplex QR skewer and the first year for this model of Simplex shift lever.
Fittings you mention for build are wildly inappropriate for this mount, but it is of course your project.
Vertically drilled bridge is slightly rare. Employed by Manufrance and a few other makers. Manufactured by NERVEX.
Lugset is by BOCAMA rather than Juy.
Stem/bar set looks to be BF.
Readers will be able to give more information with further images.
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