Could the Francesco Caracciolo class have received a Littorio-style reconstruction for the 1940s?
Short answerYes; a comprehensive machinery and protection rebuild could plausibly yield a 28-30-knot battleship compatible with the Littorio force, though the Italians would have to trade speed against torpedo defense.
NotesReplacing twenty older boilers with a smaller modern plant creates internal volume for improved torpedo protection. One option uses that space for a substantial internal defense while retaining about 28 knots. External bulges could improve protection further at the cost of reducing speed toward 26 knots. A more aggressive rebuild combines modern machinery and bulges while aiming for 30 knots and compatibility with the Littorio force. In the theoretical comparison, such a ship could fight a Queen Elizabeth and disengage if necessary, making it an urgent Royal Navy target before the Littorios were fully available.