You can use the rear O2 bungs for the wide band O2s. I have heard on here that you want them closer to the front ones but its only 2' difference and the two shops I spoke to in Dallas both said that location is fine and when they tune theirs sits in the tail pipe anyway
And no, the wide band does not connect to the factory computer. They are simply a monitoring device for you. If you are running two then you need to set up a toggle switch to switch between them if you are only running a single gauge. You then take the gauge analog output and hook it to the Livewire so you can data log.