Curious, what model falcon is best suited for the rear end to come from?

I Believe the XF falcon had a Watts Link rear with LSD, better confirm that though! oh and the ratios will be around 3.20:1 which would be a bit low.

dont get a borg warner style diff if you want to swap ratios often. i did, and i regret it. i should have got a hilux diff, as they are basicly the same as a 9inch, so easy to have another ratio set up on the shelf. borg warner to swap ratio you need to re-set pinion height, pre-load, and all that other stuff.

Xf only had 25 spline axles, better off with a later model with 28 spline and its easier to hook up an EL handbrake as it pulls inwards where as my ED handbrake pulls forward which made it abit trickier to hook up but not impossible.