are they on ebay

can get a whole diff for about $200 for a normal wreckers....so i'd say $120 for just the brakes is a bit much

cost depends on what you would do yourself
if its going onto a ute diff it just requires drilling a couple of new holes in the brackets and then welding some bits of plate into the centre of it to hold the wheel bearings in
then do brake lines to suit and might need a bias valve to get the bias right front to back

setting up the handbrake takes a bit more time and effort to get right