Typical swap is to a single wheel rear end out of a 3/4 ton or a DRW out of a 1-ton cab & chassis (C&C). The C&C housing is typically too narrow so the wheels are tucked farther in & crowd the frame rail. Your best bet is narrowing the existing housing so you can put things right where they need to be.
I would contact Todd @
http://lowboymotorsports.com/ for your slammed OBS needs.