correct offset for a 22x9.5 on a body drop

I wanted toknow if anyone had any idea as to what would be the proper offset for a 22x9.5 rim on a body dropped 89 fullsize.I am tying to get 22s for the back only and leave my 20s in the front.The tubs are high enough , my concern is the bedside rubbing.Any help would be appreciated.