biggest tires on a duster

[hardcharger426]

I know the answer is on here somewhere.
What is the biggest front tire that can fit on a 15' rim for a 71 duster with a big bolt set up????? What back spacing would you need as well??

I have a set of 15x6 ralleys with 215/70/15's and they hit the fender in the front.


thanks for the help