What were the common crew ranks on WWII US Navy flying boats and bombers?
The Navy did operate some large aircraft, notably the PB4Y-1 Liberator and PB4Y-2 Privateer, variants of the B-24 Liberator. This was a late-war addition, the first being delivered in 1944 with the majority being delivered after the war. It was difficult to find crew compositions - the best bet I had was searching for reports of crashes based off of this list, but the newspaper clippings I found did not mention any crews.
There was a post-WWII (1950) shoot-down of a Navy PB4Y-2 by the Soviets and the article does have the list of the crew members that went down, but without the crew positions (notes added based off of information here. This was an electronic intelligence flight, but the crew ranks would have been similar for the flight crew at least. Note: Navy enlisted have ranks and rates, rates being associated with their profession and as such will often be more difficult to determine where there is little information.

LT Howard W. Seeschaf

LT John H. Fette

LTJG Robert D. Reynolds

ENS Tommy L. Burgess (Ensign/O-1)

AT1 Frank L. Beckman (Avionics Electronic Technician)

AL3 Joseph J. Bourassa (Aviation Electronics Man)

AD 1 Joseph H. Danens (Aviation Machinist's Mate)

CT3 Edward J. Purcell (Communications Technician)

AN Joseph N. Rinnier (Airman)

AD 1 Jack W. Thomas (Aviation Machinist's Mate)