Actually, to keep the wheel/tire centered within the factory wheel well and, most importantly the on-center track width, the correct BS for a 9" rim is 5", then a 10" rim is 10.5".
Zero offset basically? I've always thought Mopar cars worked best with 1/2 inch of offset. So 5.5" BS on a 9 inch rim and 6.0" BS on a 10 inch rim. I usually start with 1/2 inch of offset on any Mopar I work on and then go from there. I keep a stack of spacers on the shelf so I can move the rim back out 0.125 or 0.250 to get things perfect.
