Qantas Empire Airways operated Catalinas during the war years, and if this came from a Cat, I would have thought it would have a military ref number. My best bet would be a DC3 or DC4, both operated by Qantas Empire Airways at the end of the war. After that, it was Connie's.
I'm not that familiar with US part numbers, but I am sure there is someone here who just happens to have a Douglas parts book to hand to confirm (or not) which type this was fitted to.
Cheers
ExO