Fitting a 9.2-inch gun into an eight-inch mounting

Could a 9.2-inch gun fit into an eight-inch turret position?

Possibly, if the turret ring is sufficiently wide, but the answer depends on the individual ship class.

Gun caliber alone does not decide whether the substitution works. The decisive constraint is the diameter of the existing turret ring beneath the mounting. A sufficiently wide ring might accept a redesigned 9.2-inch installation, but that would not make the change a universal drop-in refit. County-class cruisers are a possible candidate, and their dimensions would have to be checked ship class by ship class.