It is probably easiest to select a subject, then find what's available to make it up.
Coastal Command gets somewhat short shrift from manufacturers direct so you have to be creative.
First figure out what is the base B-24 model -- D or J. The D model is easy, no nose turret.
Then look at what the Lib has on it and where -- ASR, Leigh Light, rockets, etc.
Then look for a kit to fit, and baring that, a base kit and a conversion set. It is a lot easier to match to pictures than worry about which GR.? it is because there wer inconsistencies in/among them -- such as presence/absence of ASR, rockets, etc -- and lots of documentation issues. It doesn't help to be the 'Cinderella Service' ....
Here's my Hasegawa D-model (Formatting Monitor kit) with the Pavla GR.V conversion set. Note I did not use the nose ASR from the Pavla set as my refs indicated it was not on this aircraft, which was Lloyd Triggs VC aircraft. The good thing about the Hasegawa kit is that it had both US & British turrets and that made it easier.