Upgrading rear to LBP axles and drums.....

I am in the process of upgrading my 8 3/4 rear to the LBP axles and have a couple of related questions... First, when I get the LBP axles, will the flange-to-flange width of the rear change (in other words, will I need to re-check my backspacing needs for the wheels)? Second, I will need to get the 10 inch drums with the 4.5 inch BP, so I also need to replace the backing plates to accomodate the 2 1/2 brake pads, correct..?

Thanks,

Mark.