The Italians never did the mod, some say the Germans did, others say post WWII arms dealers had surpluse 8mm barrels did the mod to sell in the middle east.
Even though they say its a Mannlicher Carcano, it's a mauser type bolt with control'd round feed, it still needs the Mannlicher en-block clips to feed from the mag
I would recomend useing a mild mannerd 8mm round (velocity like a 7.65 Argentine or a 303 brit)
I had a old 6.5 with a very bad barrel and had it converted to 7.62x39mm
(AK47 round) useing a old p-14 303 enfield barrel.
the next barrel is the MKIII as thers enuf barrel shank to set it back on a carcano (303 brit and the 7.62x39 have the same case taper and easily converted, just ream in some to remove excessive freebore and its as good a shooter as any bolt gun in that caliber.
Source of new Carcano M91 clips