Most likely the stem was custom by the selling shop.
Only mess with it if you require a different length stem.
"no name" calipers were a first year of production thing. As the frame shows latter details I would not expect them.
You did well. The seat post and saddle are very uncommon, Ideale… (note Cinelli owned Unicanitor saddles)
Special Ideale alloy clamp for a plain seat post.
I think it deserves another set of wheels, high flange hubs, Fiamme tubular rims (red or yellow label), high quality tubular tires. What is one there is practical, not commanding. Red toe straps- Binda preferred.