Hopefully, you'll be able to get the u-bolt plates, the steel brake lines, and the e-brake cables from the donor rig with the IFS rear axle. Some people install wheel spacers on their front axle to make the track width equal front to rear when they install the wider axle.
Here's a site with good info on differentials and shows axle widths:
http://home.4x4wire.com/erik/diffs/

This site shows you how to read your underhood tag to find your axle ratio:
http://www.brian894x4.com/Gearratiosanddiffs.html