I'm not sure I buy this idea that the XP47H was powered by a V-16. Wasn't it powered by a radial engine?
The P-47H was powered by a Pratt & Whitney R2800 18 cylinder air cooled radial engine.
However, in the never ending quest for more speed, Republic and the Army did some testing with sleeker powerplants to improve aerodynamics by streamlining the engine cowl. Hence, the XP-47H designation for experimental.