75 Duster new brake pads won't fit

I have found that the inner pad wears faster than the outer. That's probably why they are different thicknesses.

Are you sure you are pushing the piston all the way into the caliper?

If you look at the specs from other manufacturers are they the same?

Are you sure the pads and calipers and disk are correct for your application?

What I'm getting to is are the front disks OEM to the car rather than a swap?