I did the Marine Corps version about a year ago.
These are my best guesses, because I'm not at home to look at the kit, instructions or leftover parts. I'm going by memory, but this may help.
I only used the straight lap-belts in the cabin. I used the curved belts9 through 11 for the pilot and copilot seats.
Part 19, the big plate, is armor plate that went under the fuselage just aft of the clam-shell nose doors. It's likely only appropriate for the Marine Corps version.
23 & 24 look like the pilot and copilot steps that go on the sides of the fuselage.
31 is the pitot tube.
39 & 51 look like antennas. I don't know which would be right for your SAR bird, you'd have to search references.
34, 35, and 57 - No idea, sorry.
Are parts labeled 62 the handles for the clamshell doors? I remember breaking those parts off several times. They may be best installed at the end of the build.
I hope my limited memory helps.