This information is readily available on the
QF Web Site here. But the biggest issue is around what you mean by an economy fare. A full fare economy ticket (Y class) will require 60,000 points assumeing you are starting from the Australian east coast (50,000 from Perth if using a single QF flight number).
But if you have a discount economy ticket (anything less than Y class, such as B, H, K, L, V, S, O, N etc) you will need 96,000 points from the each coast (80,000 from Perth).
Possibility of successful upgrade depends on a few things. Obviously your FF status matters and Bronze is at the bottom of the list. Your best chance is to fly on a day when there will be low demand for paid business class and high-status members upgrade requests - so try to travel mid-week and avoid Friday through Monday flights when most business travelers will be flying.