Sorry can't help on the front spacing. I never even had those figures when i purchased my wheels, i went strickly off backspacing.
However, remember, you can always take away backspacing (spacers), you can't add it. So if you spend the $$ on too little backspacing, you own 'em. Which is why i went a little more and just spaced them off some. I'd think 6 3/8 may be a little deeper than you'd like, my 5.9 just barely started touching my leaf spring, spaced 7/16" i still have plenty of 1/4 panel clearance.