I may need to be changing gears, and instead of buying gears and installing them i was thinking of buying a whole assembly. I was just curious if there was a difference in say the leaf mounts. I believe the brakes may be different, correct?

 

Depending on what truck yoiu are talking about, the widths are different with 2wd being narrower than the wider 4wd axle housings.
I dont see why the brakes would be different.

peace
Hog