Interesting about the part numbers, I can only find 55 as a prefix for AT6 parts. It must have been a standard NAA component for a while. The pump is definately P51 as it came out of the same hole as a very complete Mustang, including data plate, wing/fuselage gun selector etc. It’s in several pictures in ‘production line to frontline’ in the Osprey series. Computer is playing up and now will not upload the photo.