285's on a 10.5 in rim, while it can technically be done, will look like your putting a kids shirt on an adult (BFG says you can put a 275 tire on an 11in rim, imagine that). Your better off going with Nitto 315's in the rear. This tire is known and proven in many pics on this site to run narrower than all other 315's. Even though they are usually meant for 11's, almost everyone puts them on their 10.5's and they look nice as hell, on either size. One quick search and I found this:
http://www.ws6project.com/user_stor/...nce-315-35-17/
It's a street tire, not a drag radial and it has a 300 rating so it wont go out on you as quick as a drag radial. However, keep in mind that you cannot rotate your tires so you will be having to replace them sooner than someone that can, whether you have DR's or street tires. Just part of having a staggered set of wheels.