What Size 14" Tires? 70 Duster

In the front a 205/70/14 will fit, a 75 will be 26.1” tall but it sounds like you have taller already. A 215/70/14 should work as well.

In the back that 3.5” backspace on a 8” rim is terrible. A 225 will fit, anything wider than that and you’ll be depending on your ride height to keep the tires from hitting the body. A 235 will be close. That’s the wrong backspace for the rear, plain and simple. A duster can fit 275’s if the backspace is good.