this startet once with a pair of scope mount rings for 11 mm dovetail and a piece of T - section from a scrap box. because the 11 mm ring forgives little tolerances I made the rail from the t- section with a angle grinder and a file. polishing the rail was the most time consuming part of the work. as you see the rail was screwed on the side of an old lebel rifle, than soft soldered. in all no problem because it was clear the thing was rust blueing after. there is a pin on top of the rail behind and before the ring screw so the rings can not move when the scope is attached. in all it cost nothing beside of the money for the power.
you see the lebel have a similar receiver like the carcano so the scope is on the left side allowing the bolt handle to move.

this simple weaver sidemount will probably doing the same or better for you