I got a solid F series diff x estima from a commercial wreckers in Hams a couple of years ago, was $250 sent to TGA.
They were in Ellis Street but appear to have moved after looking at google maps.
Shouldnt be too hard to find one locally since they like to blow up all the time, Iv found the PAP website to often be inaccurate on what stock is actually in the yard.
Should swing past PAP on the 3rd and have a nosey