Cooper or Firestone

The firestones sure sound like a good tire. However the smallest size they make for 14inch rims are 215/70. I was going to use that size for the rear but I wanted 205/70 for the front two.

Would 215's fit in the front without any problems? Is there an advantage in running equal size tires all around? Such as handling?

The car is a '74 Duster.

Thanks